diff --git a/AmberTools/src/nab/nab.c b/AmberTools/src/nab/nab.c
index 5c80b67..506972a 100644
--- a/AmberTools/src/nab/nab.c
+++ b/AmberTools/src/nab/nab.c
@@ -200,7 +200,8 @@ char	nfmask[];
 {
 	int	ac;
 	char	*dotp, *amberhome;
-	char	cmd[ 1024 ], word[ 1024 ];
+	char	*cmd, word[ 1024 ];
+	int     cmd_sz;
 	int 	status;
 
     amberhome = (char *) getenv("AMBERHOME");
@@ -208,20 +209,32 @@ char	nfmask[];
        fprintf( stderr, "AMBERHOME is not set!\n" );
        exit(1);
     }
+	cmd_sz = 1024;
+	cmd = malloc(cmd_sz);
 	sprintf( cmd, "%s -I%s/include", CC, amberhome );
 	for( ac = 1; ac < argc; ac++ ){
+		word[0] = '\0';
 		if( nfmask[ ac ] ){
 			dotp = strrchr( argv[ ac ], '.' );
 			strcpy( &dotp[ 1 ], "c" );
 			sprintf( word, " %s", argv[ ac ] );
-			strcat( cmd, word );
 		}else if( argv[ ac ] ){
 			sprintf( word, " %s", argv[ ac ] );
-			strcat( cmd, word );
+		}
+		if (strlen(cmd) + strlen(word) + 1 > cmd_sz) {
+		    cmd_sz += 1024;
+		    cmd = realloc(cmd, cmd_sz);
+		}
+		if (strlen(word) > 0) {
+		    strcat( cmd, word );
 		}
 	}
 	if( !copt ){
 		sprintf( word, " -L%s/lib -lnab -lcifparse", amberhome );
+		if (strlen(cmd) + strlen(word) + strlen(FLIBS) + 7 > cmd_sz) {
+		    cmd_sz += strlen(word) + strlen(FLIBS) + 7;
+		    cmd = realloc(cmd, cmd_sz);
+		}
 		strcat( cmd, word );
 		sprintf( word, " %s ", FLIBS );
 		strcat( cmd, word );
@@ -232,4 +245,5 @@ char	nfmask[];
 	if (status != 0) {
 		fprintf(stderr,"cc failed!\n"); exit (1);
 	}
+	free(cmd);
 }