--- db-4.7.25/tcl/tcl_db.c
+++ db-4.7.25/tcl/tcl_db.c
@@ -2595,9 +2595,9 @@ tcl_DbGetFlags(interp, objc, objv, dbp)
 		for (i = 0; db_flags[i].flag != 0; i++)
 			if (LF_ISSET(db_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, db_flags[i].arg, sizeof(buf));
+				    buf, db_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));
@@ -2651,9 +2651,9 @@ tcl_DbGetOpenFlags(interp, objc, objv, dbp)
 		for (i = 0; open_flags[i].flag != 0; i++)
 			if (LF_ISSET(open_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, open_flags[i].arg, sizeof(buf));
+				    buf, open_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));
--- db-4.7.25/tcl/tcl_env.c
+++ db-4.7.25/tcl/tcl_env.c
@@ -2219,9 +2219,9 @@ env_GetFlags(interp, objc, objv, dbenv)
 		for (i = 0; open_flags[i].flag != 0; i++)
 			if (LF_ISSET(open_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, open_flags[i].arg, sizeof(buf));
+				    buf, open_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));
@@ -2282,9 +2282,9 @@ env_GetOpenFlag(interp, objc, objv, dbenv)
 		for (i = 0; open_flags[i].flag != 0; i++)
 			if (LF_ISSET(open_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, open_flags[i].arg, sizeof(buf));
+				    buf, open_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));
@@ -2334,9 +2334,9 @@ tcl_EnvGetEncryptFlags(interp, objc, objv, dbenv)
 		for (i = 0; encrypt_flags[i].flag != 0; i++)
 			if (LF_ISSET(encrypt_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, encrypt_flags[i].arg, sizeof(buf));
+				    buf, encrypt_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));
--- db-4.7.25/tcl/tcl_seq.c
+++ db-4.7.25/tcl/tcl_seq.c
@@ -497,9 +497,9 @@ tcl_SeqGetFlags(interp, objc, objv, seq)
 		for (i = 0; seq_flags[i].flag != 0; i++)
 			if (LF_ISSET(seq_flags[i].flag)) {
 				if (strlen(buf) > 0)
-					(void)strncat(buf, " ", sizeof(buf));
+					(void)strncat(buf, " ", sizeof(buf)-1);
 				(void)strncat(
-				    buf, seq_flags[i].arg, sizeof(buf));
+				    buf, seq_flags[i].arg, sizeof(buf)-1);
 			}
 
 		res = NewStringObj(buf, strlen(buf));