diff --git a/src/vapoursynth.cpp b/src/vapoursynth.cpp
index f7eeb89..de69ad5 100644
--- a/src/vapoursynth.cpp
+++ b/src/vapoursynth.cpp
@@ -50,9 +50,9 @@ static void BSInit() {
 struct BestVideoSourceData {
     VSVideoInfo VI = {};
     std::unique_ptr<BestVideoSource> V;
-    int64_t FPSNum;
-    int64_t FPSDen;
-    bool RFF;
+    int64_t FPSNum = -1;
+    int64_t FPSDen = -1;
+    bool RFF = false;
 };
 
 static const VSFrame *VS_CC BestVideoSourceGetFrame(int n, int ActivationReason, void *InstanceData, void **, VSFrameContext *FrameCtx, VSCore *Core, const VSAPI *vsapi) {
diff --git a/src/videosource.h b/src/videosource.h
index f08baf3..c16a7e8 100644
--- a/src/videosource.h
+++ b/src/videosource.h
@@ -201,7 +201,7 @@ class BestVideoSource {
     };
 private:
     struct VideoTrackIndex {
-        int64_t LastFrameDuration;
+        int64_t LastFrameDuration = 0;
         std::vector<FrameInfo> Frames;
     };