diff --git a/Makefile b/Makefile
index daed0997479..b4b35a08200 100644
--- a/Makefile
+++ b/Makefile
@@ -568,7 +568,7 @@ $(libcppdir)/checks.o: lib/checks.cpp lib/check.h lib/check64bit.h lib/checkasse
 $(libcppdir)/checksizeof.o: lib/checksizeof.cpp lib/check.h lib/checkers.h lib/checkimpl.h lib/checksizeof.h lib/config.h lib/errortypes.h lib/library.h lib/mathlib.h lib/platform.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenize.h lib/tokenlist.h lib/utils.h lib/vfvalue.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/checksizeof.cpp
 
-$(libcppdir)/checkstl.o: lib/checkstl.cpp lib/astutils.h lib/check.h lib/checkers.h lib/checkimpl.h lib/checknullpointer.h lib/checkstl.h lib/config.h lib/errortypes.h lib/library.h lib/mathlib.h lib/pathanalysis.h lib/platform.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenize.h lib/tokenlist.h lib/utils.h lib/valueflow.h lib/vfvalue.h
+$(libcppdir)/checkstl.o: lib/checkstl.cpp lib/astutils.h lib/calculate.h lib/check.h lib/checkers.h lib/checkimpl.h lib/checknullpointer.h lib/checkstl.h lib/config.h lib/errortypes.h lib/library.h lib/mathlib.h lib/pathanalysis.h lib/platform.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenize.h lib/tokenlist.h lib/utils.h lib/valueflow.h lib/vfvalue.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/checkstl.cpp
 
 $(libcppdir)/checkstring.o: lib/checkstring.cpp lib/astutils.h lib/check.h lib/checkers.h lib/checkimpl.h lib/checkstring.h lib/config.h lib/errortypes.h lib/library.h lib/mathlib.h lib/platform.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenize.h lib/tokenlist.h lib/utils.h lib/vfvalue.h
diff --git a/lib/checkstl.cpp b/lib/checkstl.cpp
index a4e8a92c188..f07e8aa7166 100644
--- a/lib/checkstl.cpp
+++ b/lib/checkstl.cpp
@@ -19,11 +19,12 @@
 #include "checkstl.h"
 
 #include "astutils.h"
+#include "calculate.h"
 #include "errortypes.h"
 #include "library.h"
 #include "mathlib.h"
-#include "refthunk.h"
 #include "pathanalysis.h"
+#include "refthunk.h"
 #include "settings.h"
 #include "standards.h"
 #include "symboldatabase.h"
@@ -1734,34 +1735,77 @@ void CheckStlImpl::checkFindInsert()
                 if (!valueTok2)
                     continue;
                 if (isSameExpression(true, valueTok, valueTok2, mSettings, true, true)) {
-                    checkFindInsertError(valueTok);
+                    // Both branches set the same value; the replacement depends on both branches, so no suggestion
+                    checkFindInsertError(valueTok, nullptr);
                 }
             } else {
-                checkFindInsertError(valueTok);
+                checkFindInsertError(valueTok, condTok);
             }
         }
     }
 }
 
-void CheckStlImpl::checkFindInsertError(const Token *tok)
-{
-    std::string replaceExpr;
-    if (tok && Token::simpleMatch(tok->astParent(), "=") && tok == tok->astParent()->astOperand2() && Token::simpleMatch(tok->astParent()->astOperand1(), "[")) {
-        if (mSettings.standards.cpp < Standards::CPP11)
-            // We will recommend using emplace/try_emplace instead
-            return;
-        const std::string f = (mSettings.standards.cpp < Standards::CPP17) ? "emplace" : "try_emplace";
-        replaceExpr = " Instead of '" + tok->astParent()->expressionString() + "' consider using '" +
-                      tok->astParent()->astOperand1()->astOperand1()->expressionString() +
-                      "." + f + "(" +
-                      tok->astParent()->astOperand1()->astOperand2()->expressionString() +
-                      ", " +
-                      tok->expressionString() +
-                      ");'.";
+/** When is the condition of the 'if' statement checked by checkFindInsert() true? */
+enum class FindInsertCond : std::uint8_t { UNKNOWN, FOUND, NOT_FOUND };
+
+static FindInsertCond getFindInsertCond(const Token* condTok)
+{
+    const Token* rhs = condTok->astOperand2();
+    if (!rhs)
+        return FindInsertCond::UNKNOWN;
+    if (Token::simpleMatch(condTok->astOperand1()->astOperand1(), ". find (")) {
+        // c.find(k) == c.end() / c.find(k) != c.end()
+        if (!Token::simpleMatch(rhs, "(") || !Token::Match(rhs->astOperand1(), ". end|cend ("))
+            return FindInsertCond::UNKNOWN;
+        if (condTok->str() == "==")
+            return FindInsertCond::NOT_FOUND;
+        if (condTok->str() == "!=")
+            return FindInsertCond::FOUND;
+        return FindInsertCond::UNKNOWN;
+    }
+    // c.count(k) == 0, c.count(k) > 0, ...: count() yields 0 or 1
+    if (!rhs->hasKnownIntValue())
+        return FindInsertCond::UNKNOWN;
+    const MathLib::bigint n = rhs->getKnownIntValue();
+    const bool found = calculate<MathLib::bigint, MathLib::bigint>(condTok->str(), 1, n) != 0;
+    const bool notFound = calculate<MathLib::bigint, MathLib::bigint>(condTok->str(), 0, n) != 0;
+    if (found == notFound)
+        return FindInsertCond::UNKNOWN;
+    return found ? FindInsertCond::FOUND : FindInsertCond::NOT_FOUND;
+}
+
+void CheckStlImpl::checkFindInsertError(const Token* tok, const Token* condTok)
+{
+    std::string suggestion;
+    std::string method = "insertion";
+    if (tok && condTok && Token::simpleMatch(tok->astParent(), "=") && tok == tok->astParent()->astOperand2() &&
+        Token::simpleMatch(tok->astParent()->astOperand1(), "[")) {
+        const std::string containerExpr = tok->astParent()->astOperand1()->astOperand1()->expressionString();
+        const std::string keyExpr = tok->astParent()->astOperand1()->astOperand2()->expressionString();
+        switch (getFindInsertCond(condTok)) {
+        case FindInsertCond::NOT_FOUND: {
+            if (mSettings.standards.cpp < Standards::CPP11)
+                // We will recommend using emplace/try_emplace instead
+                return;
+            const std::string f = (mSettings.standards.cpp < Standards::CPP17) ? "emplace" : "try_emplace";
+            suggestion = " Instead of '" + tok->astParent()->expressionString() + "' consider using '" + containerExpr +
+                         "." + f + "(" + keyExpr + ", " + tok->expressionString() + ");'.";
+            break;
+        }
+        case FindInsertCond::FOUND:
+            // The key is present, so the element is modified rather than inserted; try_emplace() would not do that
+            method = "modification";
+            suggestion = " Instead of '" + tok->astParent()->expressionString() +
+                         "' consider assigning the value through the iterator returned by '" + containerExpr +
+                         ".find(" + keyExpr + ")'.";
+            break;
+        case FindInsertCond::UNKNOWN:
+            break;
+        }
     }
+    std::string msg = "Searching before " + method + " is not necessary." + suggestion;
 
-    reportError(
-        tok, Severity::performance, "stlFindInsert", "Searching before insertion is not necessary." + replaceExpr, CWE398, Certainty::normal);
+    reportError(tok, Severity::performance, "stlFindInsert", msg, CWE398, Certainty::normal);
 }
 
 /**
@@ -3899,7 +3943,7 @@ void CheckStl::getErrorMessages(ErrorLogger& errorLogger, const Settings& settin
     c.stlBoundariesError(nullptr);
     c.if_findError(nullptr, false);
     c.if_findError(nullptr, true);
-    c.checkFindInsertError(nullptr);
+    c.checkFindInsertError(nullptr, nullptr);
     c.string_c_strError(nullptr);
     c.string_c_strReturn(nullptr);
     c.string_c_strParam(nullptr, 0);
diff --git a/lib/checkstl.h b/lib/checkstl.h
index 0f9a70a7a15..059ddb7466e 100644
--- a/lib/checkstl.h
+++ b/lib/checkstl.h
@@ -219,7 +219,8 @@ class CPPCHECKLIB CheckStlImpl : public CheckImpl {
     void sameIteratorExpressionError(const Token *tok);
     void stlBoundariesError(const Token* tok);
     void if_findError(const Token* tok, bool str);
-    void checkFindInsertError(const Token *tok);
+    /** @param condTok the comparison in the if condition, nullptr => no specific suggestion */
+    void checkFindInsertError(const Token* tok, const Token* condTok);
     void sizeError(const Token* tok);
     void redundantIfRemoveError(const Token* tok);
     void invalidContainerLoopError(const Token* tok, const Token* loopTok, ErrorPath errorPath);
diff --git a/oss-fuzz/Makefile b/oss-fuzz/Makefile
index 5b8a1d159d4..081aa035cdc 100644
--- a/oss-fuzz/Makefile
+++ b/oss-fuzz/Makefile
@@ -237,7 +237,7 @@ $(libcppdir)/checks.o: ../lib/checks.cpp ../lib/check.h ../lib/check64bit.h ../l
 $(libcppdir)/checksizeof.o: ../lib/checksizeof.cpp ../lib/check.h ../lib/checkers.h ../lib/checkimpl.h ../lib/checksizeof.h ../lib/config.h ../lib/errortypes.h ../lib/library.h ../lib/mathlib.h ../lib/platform.h ../lib/refthunk.h ../lib/settings.h ../lib/smallvector.h ../lib/sourcelocation.h ../lib/standards.h ../lib/symboldatabase.h ../lib/templatesimplifier.h ../lib/token.h ../lib/tokenize.h ../lib/tokenlist.h ../lib/utils.h ../lib/vfvalue.h
 	$(CXX) ${LIB_FUZZING_ENGINE} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/checksizeof.cpp
 
-$(libcppdir)/checkstl.o: ../lib/checkstl.cpp ../lib/astutils.h ../lib/check.h ../lib/checkers.h ../lib/checkimpl.h ../lib/checknullpointer.h ../lib/checkstl.h ../lib/config.h ../lib/errortypes.h ../lib/library.h ../lib/mathlib.h ../lib/pathanalysis.h ../lib/platform.h ../lib/refthunk.h ../lib/settings.h ../lib/smallvector.h ../lib/sourcelocation.h ../lib/standards.h ../lib/symboldatabase.h ../lib/templatesimplifier.h ../lib/token.h ../lib/tokenize.h ../lib/tokenlist.h ../lib/utils.h ../lib/valueflow.h ../lib/vfvalue.h
+$(libcppdir)/checkstl.o: ../lib/checkstl.cpp ../lib/astutils.h ../lib/calculate.h ../lib/check.h ../lib/checkers.h ../lib/checkimpl.h ../lib/checknullpointer.h ../lib/checkstl.h ../lib/config.h ../lib/errortypes.h ../lib/library.h ../lib/mathlib.h ../lib/pathanalysis.h ../lib/platform.h ../lib/refthunk.h ../lib/settings.h ../lib/smallvector.h ../lib/sourcelocation.h ../lib/standards.h ../lib/symboldatabase.h ../lib/templatesimplifier.h ../lib/token.h ../lib/tokenize.h ../lib/tokenlist.h ../lib/utils.h ../lib/valueflow.h ../lib/vfvalue.h
 	$(CXX) ${LIB_FUZZING_ENGINE} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/checkstl.cpp
 
 $(libcppdir)/checkstring.o: ../lib/checkstring.cpp ../lib/astutils.h ../lib/check.h ../lib/checkers.h ../lib/checkimpl.h ../lib/checkstring.h ../lib/config.h ../lib/errortypes.h ../lib/library.h ../lib/mathlib.h ../lib/platform.h ../lib/refthunk.h ../lib/settings.h ../lib/smallvector.h ../lib/sourcelocation.h ../lib/standards.h ../lib/symboldatabase.h ../lib/templatesimplifier.h ../lib/token.h ../lib/tokenize.h ../lib/tokenlist.h ../lib/utils.h ../lib/vfvalue.h
diff --git a/test/teststl.cpp b/test/teststl.cpp
index bb20d2d8182..1e0dd48d698 100644
--- a/test/teststl.cpp
+++ b/test/teststl.cpp
@@ -7480,6 +7480,103 @@ class TestStl : public TestFixture {
                   "}\n"); // TODO: use s?
             ASSERT_EQUALS("[test.cpp:7:17]: (performance) Searching before insertion is not necessary. Instead of 'x[5]=data' consider using 'x.try_emplace(5, data);'. [stlFindInsert]\n", errout_str());
         }
+
+        // The key is found => the value is assigned, try_emplace() would not do that
+        check("void f() {\n"
+              "    std::map<int, bool> m{{1, false}};\n"
+              "    if (m.count(1) != 0)\n"
+              "        m[1] = true;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:4:16]: (performance) Searching before modification is not necessary. Instead of 'm[1]=true' consider assigning the value through the iterator returned by 'm.find(1)'. [stlFindInsert]\n",
+            errout_str());
+
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.find(x) != m.end())\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:16]: (performance) Searching before modification is not necessary. Instead of 'm[x]=1' consider assigning the value through the iterator returned by 'm.find(x)'. [stlFindInsert]\n",
+            errout_str());
+
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.count(x) > 0)\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:16]: (performance) Searching before modification is not necessary. Instead of 'm[x]=1' consider assigning the value through the iterator returned by 'm.find(x)'. [stlFindInsert]\n",
+            errout_str());
+
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.count(x) == 1)\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:16]: (performance) Searching before modification is not necessary. Instead of 'm[x]=1' consider assigning the value through the iterator returned by 'm.find(x)'. [stlFindInsert]\n",
+            errout_str());
+
+        // The key is not found => try_emplace()
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.count(x) == 0)\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:16]: (performance) Searching before insertion is not necessary. Instead of 'm[x]=1' consider using 'm.try_emplace(x, 1);'. [stlFindInsert]\n",
+            errout_str());
+
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.count(x) < 1)\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:16]: (performance) Searching before insertion is not necessary. Instead of 'm[x]=1' consider using 'm.try_emplace(x, 1);'. [stlFindInsert]\n",
+            errout_str());
+
+        // Unknown condition => no suggestion
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x, unsigned y) {\n"
+              "    if (m.count(x) == y)\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3:16]: (performance) Searching before insertion is not necessary. [stlFindInsert]\n",
+                      errout_str());
+
+        // Both branches set the value => no suggestion
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.find(x) == m.end())\n"
+              "        m[x] = 1;\n"
+              "    else\n"
+              "        m[x] = 1;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3:16]: (performance) Searching before insertion is not necessary. [stlFindInsert]\n",
+                      errout_str());
+
+        check("void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+              "    if (m.find(x) != m.end())\n"
+              "        m[x] = 1;\n"
+              "    else\n"
+              "        m.emplace(x, 1);\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3:16]: (performance) Searching before insertion is not necessary. [stlFindInsert]\n",
+                      errout_str());
+
+        // The suggestion for a found key does not depend on the C++ standard
+        {
+            Settings s = settings;
+            const char code[] = "void f(std::map<unsigned, unsigned>& m, unsigned x) {\n"
+                                "    if (m.count(x) != 0)\n"
+                                "        m[x] = 1;\n"
+                                "}\n";
+            s.standards.cpp = Standards::CPP03;
+            check(code, s);
+            ASSERT_EQUALS(
+                "[test.cpp:3:16]: (performance) Searching before modification is not necessary. Instead of 'm[x]=1' consider assigning the value through the iterator returned by 'm.find(x)'. [stlFindInsert]\n",
+                errout_str());
+            s.standards.cpp = Standards::CPP11;
+            check(code, s);
+            ASSERT_EQUALS(
+                "[test.cpp:3:16]: (performance) Searching before modification is not necessary. Instead of 'm[x]=1' consider assigning the value through the iterator returned by 'm.find(x)'. [stlFindInsert]\n",
+                errout_str());
+        }
     }
 
     void checkKnownEmptyContainer() {