diff --git a/mac/Keyman4MacIM/make-km-dmg.sh b/mac/Keyman4MacIM/make-km-dmg.sh
index b79f40e8b48..b6a3ae38f69 100755
--- a/mac/Keyman4MacIM/make-km-dmg.sh
+++ b/mac/Keyman4MacIM/make-km-dmg.sh
@@ -190,11 +190,17 @@ displayInfo "Detaching \"$WORKING_COPY_OF_IMAGE\""
 # because macOS may still be working in the folder in the
 # background
 DETACH_SUCCESS=0
+DETACH_FORCE=
 while (( DETACH_SUCCESS < 10 )); do
-    hdiutil detach $STAGING_DIR $VERBOSITY
-    if  [[ $? != 0 || -d "$STAGING_DIR" ]] ; then
+    DETACH_RESULT=0
+    hdiutil detach $STAGING_DIR $VERBOSITY $DETACH_FORCE || DETACH_RESULT=$?
+    if  [[ $DETACH_RESULT != 0 || -d "$STAGING_DIR" ]] ; then
         (( DETACH_SUCCESS++ ))
         echo "Failed to unmount: \"$STAGING_DIR\" on attempt #$DETACH_SUCCESS. Waiting 5 seconds to try again."
+        if (( DETACH_SUCCESS > 5 )); then
+            echo "  Note: Detach failed first five times, so now attempting with '-force'"
+            DETACH_FORCE=-force
+        fi
         sleep 5
     else
         DETACH_SUCCESS=999