diff --git a/src/d_dehacked.cpp b/src/d_dehacked.cpp
index 508821fd8..2e8c56f05 100644
--- a/src/d_dehacked.cpp
+++ b/src/d_dehacked.cpp
@@ -1475,7 +1475,7 @@ static int PatchFrame (int frameNum)
 		info->Misc1 = misc1;
 		info->Frame = frame & 0x3f;
 		if (frame & 0x8000) info->StateFlags |= STF_FULLBRIGHT;
-		else info->StateFlags &= STF_FULLBRIGHT;
+		else info->StateFlags &= ~STF_FULLBRIGHT;
 	}
 
 	return result;
diff --git a/src/p_states.cpp b/src/p_states.cpp
index 5444bcc3a..6e45db6b0 100644
--- a/src/p_states.cpp
+++ b/src/p_states.cpp
@@ -938,13 +938,13 @@ int FStateDefinitions::AddStates(FState *state, const char *framechars, const FS
 
 		state->Frame = frame;
 		if (noframe) state->StateFlags |= STF_SAMEFRAME;
-		else state->StateFlags &= STF_SAMEFRAME;
+		else state->StateFlags &= ~STF_SAMEFRAME;
 		StateArray.Push(*state);
 		SourceLines.Push(sc);
 		++count;
 
 		// NODELAY flag is not carried past the first state
-		state->StateFlags &= STF_NODELAY;
+		state->StateFlags &= ~STF_NODELAY;
 	}
 	laststate = &StateArray[StateArray.Size() - 1];
 	laststatebeforelabel = laststate;