diff --git a/hw/xquartz/darwin.c b/hw/xquartz/darwin.c
index aba4869f8..d5d29b123 100644
--- a/hw/xquartz/darwin.c
+++ b/hw/xquartz/darwin.c
@@ -519,13 +519,19 @@ InitInput(int argc, char **argv)
         .rules   = "base", .model         = "empty", .layout = "empty",
         .variant = NULL,   .options       = NULL
     };
+    int result;
 
     /* We need to really have rules... or something... */
     XkbSetRulesDflts(&rmlvo);
 
-    assert(Success == AllocDevicePair(serverClient, "xquartz virtual",
-                                      &darwinPointer, &darwinKeyboard,
-                                      DarwinMouseProc, DarwinKeybdProc, FALSE));
+    result = AllocDevicePair(serverClient, "xquartz virtual",
+                             &darwinPointer, &darwinKeyboard,
+                             DarwinMouseProc, DarwinKeybdProc, FALSE);
+    if (result != Success) {
+        FatalError("InitInput: AllocDevicePair (...,\"xquartz virtual\",...) "
+                   "returned X windows error %d.\n",
+                   result);
+    }
 
     /* here's the snippet from the current gdk sources:
        if (!strcmp (tmp_name, "pointer"))
@@ -542,15 +548,26 @@ InitInput(int argc, char **argv)
      */
 
     darwinTabletStylus = AddInputDevice(serverClient, DarwinTabletProc, TRUE);
-    assert(darwinTabletStylus);
+    if (!darwinTabletStylus) {
+        FatalError("InitInput: "
+                   "AddInputDevice(serverClient, DarwinTabletProc, TRUE) "
+                   "failed.\n");
+    }
+
     darwinTabletStylus->name = strdup("pen");
 
     darwinTabletCursor = AddInputDevice(serverClient, DarwinTabletProc, TRUE);
-    assert(darwinTabletCursor);
+    if(!darwinTabletCursor) {
+        FatalError("InitInput: "
+                   "AddInputDevice(serverClient, DarwinTabletProc, TRUE) "
+                   "failed.\n");
+    }
     darwinTabletCursor->name = strdup("cursor");
 
     darwinTabletEraser = AddInputDevice(serverClient, DarwinTabletProc, TRUE);
-    assert(darwinTabletEraser);
+    if(!darwinTabletEraser) {
+        FatalError("InitInput: AddInputDevice(serverClient, DarwinTabletProc, TRUE) failed.\n");
+    }
     darwinTabletEraser->name = strdup("eraser");
 
     DarwinEQInit();
@@ -679,8 +696,18 @@ OsVendorInit(void)
     if (serverGeneration == 1) {
         char *lf;
         char *home = getenv("HOME");
-        assert(home);
-        assert(0 < asprintf(&lf, "%s/Library/Logs/X11", home));
+        int nbytes;
+
+        if (!home) {
+            FatalError("darwin OsVendorInit: "
+                       "getenv(\"HOME\") returned NULL.\n");
+        }
+
+        nbytes = asprintf(&lf, "%s/Library/Logs/X11", home);
+        if (nbytes <= 0) {
+            FatalError("darwin OsVendorInit: "
+                       "asprintf of log directory name failed.\n");
+        }
 
         /* Ignore errors.  If EEXIST, we don't care.  If anything else,
          * LogInit will handle it for us.
@@ -688,9 +715,12 @@ OsVendorInit(void)
         (void)mkdir(lf, S_IRWXU | S_IRWXG | S_IRWXO);
         free(lf);
 
-        assert(0 <
-               asprintf(&lf, "%s/Library/Logs/X11/%s.log", home,
-                        bundle_id_prefix));
+        nbytes = asprintf(&lf, "%s/Library/Logs/X11/%s.log", home,
+                          bundle_id_prefix);
+        if (nbytes <= 0) {
+            FatalError("darwin OsVendorInit: "
+                       "asprintf of log file name failed.\n");
+        }
         LogInit(lf, ".old");
         free(lf);