diff --git a/lib/icinga/pluginutility.cpp b/lib/icinga/pluginutility.cpp
index 8ce301ac8..15189f7b9 100644
--- a/lib/icinga/pluginutility.cpp
+++ b/lib/icinga/pluginutility.cpp
@@ -70,10 +70,17 @@ void PluginUtility::ExecuteCommand(const Command::Ptr& commandObj, const Checkab
 		for (const Dictionary::Pair& kv : env) {
 			String name = kv.second;
 
+			String missingMacro;
 			Value value = MacroProcessor::ResolveMacros(name, macroResolvers, cr,
-				nullptr, MacroProcessor::EscapeCallback(), resolvedMacros,
+				&missingMacro, MacroProcessor::EscapeCallback(), resolvedMacros,
 				useResolvedMacros);
 
+#ifdef I2_DEBUG
+			if (!missingMacro.IsEmpty())
+				Log(LogDebug, "PluginUtility")
+					<< "Macro '" << name << "' is not defined.";
+#endif /* I2_DEBUG */
+
 			if (value.IsObjectType<Array>())
 				value = Utility::Join(value, ';');