diff --git a/src/shared/proparser/qmakebuiltins.cpp b/src/shared/proparser/qmakebuiltins.cpp
index 8cf510f79c2..a09f26c8009 100644
--- a/src/shared/proparser/qmakebuiltins.cpp
+++ b/src/shared/proparser/qmakebuiltins.cpp
@@ -1044,8 +1044,10 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateConditionalFunction(
         // ### Consider real termination in non-cumulative mode
         return returnBool(function != QLatin1String("error"));
     }
-#if 0 // Way too dangerous to enable.
+#ifdef PROEVALUATOR_FULL
     case T_SYSTEM: {
+        if (m_cumulative) // Anything else would be insanity
+            return ReturnFalse;
         if (args.count() != 1) {
             evalError(fL1S("system(exec) requires one argument."));
             return ReturnFalse;
diff --git a/tests/manual/proparser/testreader.pro b/tests/manual/proparser/testreader.pro
index ced4ccc265d..6d58c9e257d 100644
--- a/tests/manual/proparser/testreader.pro
+++ b/tests/manual/proparser/testreader.pro
@@ -23,4 +23,4 @@ DEFINES += QMAKE_BUILTIN_PRFS
 
 DEFINES += QT_NO_CAST_TO_ASCII QT_NO_CAST_FROM_ASCII
 DEFINES += QT_USE_FAST_OPERATOR_PLUS QT_USE_FAST_CONCATENATION
-DEFINES += PROEVALUATOR_CUMULATIVE PROEVALUATOR_INIT_PROPS
+DEFINES += PROEVALUATOR_FULL PROEVALUATOR_CUMULATIVE PROEVALUATOR_INIT_PROPS