diff --git a/lib/templatesimplifier.cpp b/lib/templatesimplifier.cpp
index 8b4a0fa1c..0beb610d1 100644
--- a/lib/templatesimplifier.cpp
+++ b/lib/templatesimplifier.cpp
@@ -626,13 +626,26 @@ void TemplateSimplifier::deleteToken(Token *tok)
         tok->deleteThis();
 }
 
-bool TemplateSimplifier::removeTemplate(Token *tok)
+static void invalidateForwardDecls(const Token* beg, const Token* end, std::map<Token*, Token*>* forwardDecls) {
+    if (!forwardDecls)
+        return;
+    for (auto& fwd : *forwardDecls) {
+        for (const Token* tok = beg; tok != end; tok = tok->next())
+            if (fwd.second == tok) {
+                fwd.second = nullptr;
+                break;
+            }
+    }
+}
+
+bool TemplateSimplifier::removeTemplate(Token *tok, std::map<Token*, Token*>* forwardDecls)
 {
     if (!Token::simpleMatch(tok, "template <"))
         return false;
 
     Token *end = findTemplateDeclarationEnd(tok);
     if (end && end->next()) {
+        invalidateForwardDecls(tok, end->next(), forwardDecls);
         eraseTokens(tok, end->next());
         deleteToken(tok);
         return true;
@@ -2417,8 +2430,10 @@ static void invalidateInst(const Token* beg, const Token* end, std::vector<newIn
         return;
     for (auto& inst : *newInst) {
         for (const Token* tok = beg; tok != end; tok = tok->next())
-            if (inst.token == tok)
+            if (inst.token == tok) {
                 inst.token = nullptr;
+                break;
+            }
     }
 }
 
@@ -3850,8 +3865,8 @@ void TemplateSimplifier::simplifyTemplates(
                     // remove forward declaration if found
                     auto it1 = mTemplateForwardDeclarationsMap.find(it->token());
                     if (it1 != mTemplateForwardDeclarationsMap.end())
-                        removeTemplate(it1->second);
-                    removeTemplate(it->token());
+                        removeTemplate(it1->second, &mTemplateForwardDeclarationsMap);
+                    removeTemplate(it->token(), &mTemplateForwardDeclarationsMap);
                 }
                 mTemplateDeclarations.erase(decl);
             }
diff --git a/lib/templatesimplifier.h b/lib/templatesimplifier.h
index a454b092e..b0e373bf3 100644
--- a/lib/templatesimplifier.h
+++ b/lib/templatesimplifier.h
@@ -457,7 +457,7 @@ private:
     /**
      * Remove a specific "template < ..." template class/function
      */
-    static bool removeTemplate(Token *tok);
+    static bool removeTemplate(Token *tok, std::map<Token*, Token*>* forwardDecls = nullptr);
 
     /** Syntax error */
     NORETURN static void syntaxError(const Token *tok);
diff --git a/test/testsimplifytemplate.cpp b/test/testsimplifytemplate.cpp
index 4307e45c7..e3db648b0 100644
--- a/test/testsimplifytemplate.cpp
+++ b/test/testsimplifytemplate.cpp
@@ -4054,6 +4054,26 @@ private:
                             "b<a100<int>> d100;";
         // don't bother checking the output because this is not instantiated properly
         tok(code); // don't crash
+
+        const char code2[] = "template<typename T> void f();\n" // #11489
+                             "template<typename T> void f(int);\n"
+                             "void g() {\n"
+                             "    f<int>();\n"
+                             "    f<char>(1);\n"
+                             "}\n"
+                             "template<typename T>\n"
+                             "void f(int) {}\n"
+                             "template<typename T>\n"
+                             "void f() {\n"
+                             "    f<T>(0);\n"
+                             "}\n";
+        const char exp2[] = "template < typename T > void f ( ) ; "
+                            "void f<int> ( int ) ; "
+                            "void f<char> ( int ) ; "
+                            "void g ( ) { f<int> ( ) ; f<char> ( 1 ) ; } "
+                            "void f<int> ( ) { f<int> ( 0 ) ; } "
+                            "void f<char> ( int ) { }";
+        ASSERT_EQUALS(exp2, tok(code2));
     }
 
     void template159() {  // #9886