diff --git a/doc/Changelog b/doc/Changelog
index 1f788f683..ebbfcead8 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -2,6 +2,8 @@
 	- Merge #909 from headshog: Numeric truncation when parsing TYPEXX and
 	  CLASSXX representation.
 	- For #909: Fix return values.
+	- Merge #901 from Sergei Trofimovich: config: improve handling of
+	  unknown modules.
 
 14 July 2023: George
 	- More clear description of the different auth-zone behaviors on the
diff --git a/services/modstack.c b/services/modstack.c
index da8e623c1..a90d7178c 100644
--- a/services/modstack.c
+++ b/services/modstack.c
@@ -120,12 +120,16 @@ modstack_config(struct module_stack* stack, const char* module_conf)
 		stack->mod[i] = module_factory(&module_conf);
 		if(!stack->mod[i]) {
 			char md[256];
+			char * s = md;
 			snprintf(md, sizeof(md), "%s", module_conf);
-			if(strchr(md, ' ')) *(strchr(md, ' ')) = 0;
-			if(strchr(md, '\t')) *(strchr(md, '\t')) = 0;
+			/* Leading spaces are present on errors. */
+			while (*s && isspace((unsigned char)*s))
+				s++;
+			if(strchr(s, ' ')) *(strchr(s, ' ')) = 0;
+			if(strchr(s, '\t')) *(strchr(s, '\t')) = 0;
 			log_err("Unknown value in module-config, module: '%s'."
 				" This module is not present (not compiled in),"
-				" See the list of linked modules with unbound -V", md);
+				" See the list of linked modules with unbound -V", s);
 			return 0;
 		}
 	}