diff --git a/Dockerfile b/Dockerfile
index 919d183..d4f54bb 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -55,25 +55,23 @@ RUN \
         pattern="fixme:win:NtUserLockWindowUpdate ((nil))"; \
         # The amount of times the pattern should occur for the process to be considered stuck
         patternCount=2; \
-        output="$( \
-            sed \
-                # Handle exit hints
-                -e "s/^exit \([[:digit:]]\+\)$/\1/; t end;" \
-                # Handle multiple occurrences of $pattern
-                -e "/$pattern/{ x; s/^x\{$(expr $patternCount - 1)\}$/\0/; t stuck; s/^\(x*\)$/\1x/; x; };" \
-                # Delete output and return to start
-                -e "d; b;" \
-                # Branch "stuck": delete output and exit with code 42
-                -e ":stuck s/.*//; q42;" \
-                # Branch "end": exit with code 0
-                -e ":end q;")"; \
+        sed \
+            -u \
+            # Handle multiple occurrences of $pattern
+            -e "/$pattern/{ x; s/^x\{$(expr $patternCount - 1)\}$/\0/; t stuck; s/^\(x*\)$/\1x/; x; };" \
+            # Delete output and return to start
+            -e "b;" \
+            # Branch "stuck": delete output and exit with code 42
+            -e ":stuck q42;" \
+            # Branch "end": exit with code 0
+            -e ":end q;"; \
         exitCode="$?"; \
         # Kill installer if it got stuck (according to console output)
         [ "$exitCode" -eq 42 ] && pkill -9 MDK537.exe; \
         # Use `sed`s exit code if non-zero
-        [ "$exitCode" -ne 0 ] && exit $exitCode; \
-        # Use `sed`s output otherwise
-        [ "$exitCode" -eq 0 ] && exit $output; \
+        [ "$exitCode" -ne 0 ] && exit "$exitCode" || \
+        # Return true otherwise
+        true; \
     }; \
     # Run actual MDK537 installer
     install_keil() { \
@@ -82,11 +80,22 @@ RUN \
         logFile="$(mktemp)"; \
         # Run installer asynchronously
         { \
-            { 2>&1 WINEDEBUG=+all,trace-all,warn-all /usr/bin/entrypoint wine MDK537.exe --batch-install || echo "exit $?"; } \
-                # Write output to `log.txt`
-                | { [ "$DEBUG" -eq 1 ] && tee "$logFile" || cat; } \
-                # Pipe stdout and stderr to `handle_output` function
-                | handle_output & \
+            { \
+                local exitCode; \
+                exitCodeFile="$(mktemp)"; \
+                { \
+                    2>&1 WINEDEBUG=+all,trace-all,warn-all /usr/bin/entrypoint wine MDK537.exe --batch-install; \
+                    echo "$?" > "$exitCodeFile"; \
+                } \
+                    # Write output to a log file when debugging
+                    | { [ "$DEBUG" -eq 1 ] && tee "$logFile" || cat; } \
+                    # Pipe stdout and stderr to `handle_output` function
+                    | handle_output; \
+                outputHandlerCode="$?"; \
+                exitCode="$(cat "$exitCodeFile")"; \
+                rm "$exitCodeFile"; \
+                bash -c "exit $([ "$outputHandlerCode" -ne 0 ] && "$outputHandlerCode" || "$exitCode")"; \
+            } & \
         }; \
         pid="$!"; \
         # Continuously display screenshots and iteration number