diff --git a/dlls/winmm/lolvldrv.c b/dlls/winmm/lolvldrv.c
index e0bf737e2f..d50f329633 100644
--- a/dlls/winmm/lolvldrv.c
+++ b/dlls/winmm/lolvldrv.c
@@ -763,10 +763,16 @@ void    MMDRV_Exit(void)
         MMDRV_ExitPerType(&MMDrvs[i], MMDRV_WAVEOUT);
         CloseDriver(MMDrvs[i].hDriver, 0, 0);
     }
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_AUX].lpMlds - 1);
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIXER].lpMlds - 1);
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIDIIN].lpMlds - 1);
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIDIOUT].lpMlds - 1);
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_WAVEIN].lpMlds - 1);
-    HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_WAVEOUT].lpMlds - 1);
+    if (llTypes[MMDRV_AUX].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_AUX].lpMlds - 1);
+    if (llTypes[MMDRV_MIXER].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIXER].lpMlds - 1);
+    if (llTypes[MMDRV_MIDIIN].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIDIIN].lpMlds - 1);
+    if (llTypes[MMDRV_MIDIOUT].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_MIDIOUT].lpMlds - 1);
+    if (llTypes[MMDRV_WAVEIN].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_WAVEIN].lpMlds - 1);
+    if (llTypes[MMDRV_WAVEOUT].lpMlds)
+        HeapFree(GetProcessHeap(), 0, llTypes[MMDRV_WAVEOUT].lpMlds - 1);
 }