diff --git a/lib/checkunusedfunctions.cpp b/lib/checkunusedfunctions.cpp
index e8cc100f3..b864d6cd6 100644
--- a/lib/checkunusedfunctions.cpp
+++ b/lib/checkunusedfunctions.cpp
@@ -75,6 +75,9 @@ void CheckUnusedFunctions::parseTokens(const Tokenizer &tokenizer, const char Fi
         if (func->isAttributeConstructor() || func->isAttributeDestructor() || func->type != Function::eFunction || func->isOperator())
             continue;
 
+        if (func->isExtern())
+            continue;
+
         // Don't care about templates
         if (tokenizer.isCPP() && func->templateDef != nullptr)
             continue;
diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index a877fbd2b..815f92188 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -2451,7 +2451,7 @@ const Token *Function::setFlags(const Token *tok1, const Scope *scope)
             isInlineKeyword(true);
 
         // extern function
-        if (tok1->str() == "extern") {
+        if (tok1->isExternC() || tok1->str() == "extern") {
             isExtern(true);
         }
 
diff --git a/test/testunusedfunctions.cpp b/test/testunusedfunctions.cpp
index 060da66f7..e2cd170f6 100644
--- a/test/testunusedfunctions.cpp
+++ b/test/testunusedfunctions.cpp
@@ -394,6 +394,10 @@ private:
         // Don't crash on wrong syntax
         check("int x __attribute__((constructor));\n"
               "int y __attribute__((destructor));");
+
+        // #10661
+        check("extern \"C\" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t dataSize) { return 0; }\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void initializer_list() {