diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 07c914791..f43cceb60 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -681,9 +681,9 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
                     const Variable* var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(tok2->varId());
                     if (var && var->nameToken() == tok2) { // Declaration: Skip
                         tok = tok2->next();
-                        if (tok && Token::Match(tok, "( %var% )")) // Simple initialization through copy ctor
+                        if (Token::Match(tok, "( %var% )")) // Simple initialization through copy ctor
                             tok = tok->next();
-                        else if (tok && Token::Match(tok, "= %var% ;")) // Simple initialization
+                        else if (Token::Match(tok, "= %var% ;")) // Simple initialization
                             tok = tok->next();
                         else if (var->typeEndToken()->str() == ">") // Be careful with types like std::vector
                             tok = tok->previous();
@@ -885,7 +885,7 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
                  Token::Match(tok->next(), "%var%") && !Token::Match(tok->next(), "true|false|new") && tok->strAt(2) != "=")
             variables.readAll(tok->next()->varId());
 
-        else if (Token::Match(tok, "%var%") && (tok->next()->str() == ")" || tok->next()->isExtendedOp()))
+        else if (Token::Match(tok, "%var%") && tok->next() && (tok->next()->str() == ")" || tok->next()->isExtendedOp()))
             variables.readAll(tok->varId());
 
         else if (Token::Match(tok, "%var% ;") && Token::Match(tok->previous(), "[;{}:]"))
@@ -908,9 +908,10 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
         else if (tok->isAssignmentOp()) {
             for (const Token *tok2 = tok->next(); tok2 && tok2->str() != ";"; tok2 = tok2->next()) {
                 if (tok2->varId()) {
-                    variables.read(tok2->varId());
                     if (tok2->next()->isAssignmentOp())
                         variables.write(tok2->varId());
+                    else
+                        variables.read(tok2->varId());
                 }
             }
         }
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 7b449e4ea..158e4d334 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -142,6 +142,8 @@ private:
         TEST_CASE(localvarIfNOT);    // #3104 - if ( NOT var )
         TEST_CASE(localvarAnd);      // #3672
         TEST_CASE(localvarSwitch);   // #3744 - false positive when localvar is used in switch
+
+        TEST_CASE(crash1);
     }
 
     void checkStructMemberUsage(const char code[]) {
@@ -3192,6 +3194,13 @@ private:
         // Don't write an error that "a" is not used
         ASSERT_EQUALS("", errout.str());
     }
+
+    void crash1() {
+        functionVariableUsage("SAL_WNODEPRECATED_DECLARATIONS_PUSH\n"
+                              "void convertToTokenArray() {\n"
+                              "}\n"
+                              "SAL_WNODEPRECATED_DECLARATIONS_POP"); // #4033
+    }
 };
 
 REGISTER_TEST(TestUnusedVar)