diff --git a/lib/asn1/lex.l b/lib/asn1/lex.l
index 4554a9477..5dca8c828 100644
--- a/lib/asn1/lex.l
+++ b/lib/asn1/lex.l
@@ -286,7 +286,7 @@ WITH			{ return kw_WITH; }
 %%
 
 int
-yywrap ()
+yywrap (void)
 {
      return 1;
 }
diff --git a/lib/com_err/lex.l b/lib/com_err/lex.l
index e812b32df..fc73bf952 100644
--- a/lib/com_err/lex.l
+++ b/lib/com_err/lex.l
@@ -72,7 +72,7 @@ end			{ return END; }
 %%
 
 int
-yywrap ()
+yywrap (void)
 {
      return 1;
 }
diff --git a/lib/hx509/sel-lex.l b/lib/hx509/sel-lex.l
index f401e40e3..eeef9665d 100644
--- a/lib/hx509/sel-lex.l
+++ b/lib/hx509/sel-lex.l
@@ -125,7 +125,7 @@ handle_string(void)
 #endif
 
 int
-yywrap ()
+yywrap (void)
 {
      return 1;
 }
diff --git a/lib/sl/slc-lex.l b/lib/sl/slc-lex.l
index 3a3730233..e7ddcd27c 100644
--- a/lib/sl/slc-lex.l
+++ b/lib/sl/slc-lex.l
@@ -152,7 +152,7 @@ handle_string(void)
 }
 
 int
-yywrap ()
+yywrap (void)
 {
      return 1;
 }