diff --git a/src/cmd/5a/lex.c b/src/cmd/5a/lex.c
index 44ce3bb403..540c12af59 100644
--- a/src/cmd/5a/lex.c
+++ b/src/cmd/5a/lex.c
@@ -139,9 +139,10 @@ main(int argc, char *argv[])
 int
 assemble(char *file)
 {
-	char ofile[100], incfile[20], *p;
+	char *ofile, incfile[20], *p;
 	int i, of;
 
+	ofile = alloc(strlen(file)+3); // +3 for .x\0 (x=thechar)
 	strcpy(ofile, file);
 	p = utfrrune(ofile, '/');
 	if(p) {
diff --git a/src/cmd/6a/a.h b/src/cmd/6a/a.h
index 11ace63899..f1a0453156 100644
--- a/src/cmd/6a/a.h
+++ b/src/cmd/6a/a.h
@@ -168,6 +168,7 @@ EXTERN	char*	thestring;
 EXTERN	int32	thunk;
 EXTERN	Biobuf	obuf;
 
+void*   alloc(int32);
 void*	allocn(void*, int32, int32);
 void	errorexit(void);
 void	pushio(void);
diff --git a/src/cmd/6a/lex.c b/src/cmd/6a/lex.c
index 7621021c4f..a1814b0805 100644
--- a/src/cmd/6a/lex.c
+++ b/src/cmd/6a/lex.c
@@ -139,9 +139,10 @@ main(int argc, char *argv[])
 int
 assemble(char *file)
 {
-	char ofile[100], incfile[20], *p;
+	char *ofile, incfile[20], *p;
 	int i, of;
 
+	ofile = alloc(strlen(file)+3); // +3 for .x\0 (x=thechar)
 	strcpy(ofile, file);
 	p = utfrrune(ofile, pathchar());
 	if(p) {
diff --git a/src/cmd/8a/a.h b/src/cmd/8a/a.h
index bf0fc77083..c019ce4d66 100644
--- a/src/cmd/8a/a.h
+++ b/src/cmd/8a/a.h
@@ -169,6 +169,7 @@ EXTERN	char*	thestring;
 EXTERN	int32	thunk;
 EXTERN	Biobuf	obuf;
 
+void*   alloc(int32);
 void*	allocn(void*, int32, int32);
 void	errorexit(void);
 void	pushio(void);
diff --git a/src/cmd/8a/lex.c b/src/cmd/8a/lex.c
index a426713427..a00ac49f6c 100644
--- a/src/cmd/8a/lex.c
+++ b/src/cmd/8a/lex.c
@@ -138,9 +138,10 @@ main(int argc, char *argv[])
 int
 assemble(char *file)
 {
-	char ofile[100], incfile[20], *p;
+	char *ofile, incfile[20], *p;
 	int i, of;
 
+	ofile = alloc(strlen(file)+3); // +3 for .x\0 (x=thechar)
 	strcpy(ofile, file);
 	p = utfrrune(ofile, pathchar());
 	if(p) {