diff --git a/renderdoc/api/replay/data_types.h b/renderdoc/api/replay/data_types.h
index 582b3bb59..b22f3c1c8 100644
--- a/renderdoc/api/replay/data_types.h
+++ b/renderdoc/api/replay/data_types.h
@@ -1388,16 +1388,16 @@ DOCUMENT("Contains the bytes and metadata describing a thumbnail.");
 struct Thumbnail
 {
   DOCUMENT("The :class:`FileType` of the data in the thumbnail.");
-  FileType type;
+  FileType type = FileType::Raw;
 
   DOCUMENT("The ``bytes`` byte array containing the raw data.");
   bytebuf data;
 
   DOCUMENT("The width of the thumbnail image.");
-  uint32_t width;
+  uint32_t width = 0;
 
   DOCUMENT("The height of the thumbnail image.");
-  uint32_t height;
+  uint32_t height = 0;
 };
 
 DECLARE_REFLECTION_STRUCT(Thumbnail);
diff --git a/renderdoc/api/replay/shader_types.h b/renderdoc/api/replay/shader_types.h
index 71a00c3e9..198725028 100644
--- a/renderdoc/api/replay/shader_types.h
+++ b/renderdoc/api/replay/shader_types.h
@@ -122,7 +122,7 @@ struct ShaderVariable
   {
     name = "";
     rows = columns = 0;
-    displayAsHex = isStruct = false;
+    displayAsHex = isStruct = rowMajor = false;
     type = VarType::Float;
     for(int i = 0; i < 16; i++)
       value.uv[i] = 0;
@@ -132,7 +132,7 @@ struct ShaderVariable
     name = n;
     rows = 1;
     columns = 4;
-    displayAsHex = isStruct = false;
+    displayAsHex = isStruct = rowMajor = false;
     for(int i = 0; i < 16; i++)
       value.uv[i] = 0;
     type = VarType::Float;
@@ -146,7 +146,7 @@ struct ShaderVariable
     name = n;
     rows = 1;
     columns = 4;
-    displayAsHex = isStruct = false;
+    displayAsHex = isStruct = rowMajor = false;
     for(int i = 0; i < 16; i++)
       value.uv[i] = 0;
     type = VarType::Int;
@@ -160,7 +160,7 @@ struct ShaderVariable
     name = n;
     rows = 1;
     columns = 4;
-    displayAsHex = isStruct = false;
+    displayAsHex = isStruct = rowMajor = false;
     for(int i = 0; i < 16; i++)
       value.uv[i] = 0;
     type = VarType::UInt;
diff --git a/renderdoc/core/replay_proxy.h b/renderdoc/core/replay_proxy.h
index 73038ad47..c5d222b1f 100644
--- a/renderdoc/core/replay_proxy.h
+++ b/renderdoc/core/replay_proxy.h
@@ -640,7 +640,7 @@ private:
   // m_Replay is set
   uint64_t m_PreviewOutput = 0;
   // The previous windowing data, so we can detect changes and recreate the window
-  WindowingData m_PreviewWindowingData;
+  WindowingData m_PreviewWindowingData = {WindowingSystem::Unknown};
 
   uint32_t m_EventID = 0;
 
diff --git a/renderdoc/driver/d3d11/d3d11_rendertext.cpp b/renderdoc/driver/d3d11/d3d11_rendertext.cpp
index c9bce1565..2ddd86ef5 100644
--- a/renderdoc/driver/d3d11/d3d11_rendertext.cpp
+++ b/renderdoc/driver/d3d11/d3d11_rendertext.cpp
@@ -296,7 +296,7 @@ void D3D11TextRenderer::RenderTextInternal(float x, float y, const char *text)
 
   RDCASSERT(strlen(text) < FONT_MAX_CHARS);
 
-  FontCBuffer data;
+  FontCBuffer data = {};
 
   data.TextPosition.x = x;
   data.TextPosition.y = y;
diff --git a/renderdoc/driver/d3d12/d3d12_rendertext.cpp b/renderdoc/driver/d3d12/d3d12_rendertext.cpp
index 025ecf7ce..2f8110057 100644
--- a/renderdoc/driver/d3d12/d3d12_rendertext.cpp
+++ b/renderdoc/driver/d3d12/d3d12_rendertext.cpp
@@ -442,7 +442,7 @@ void D3D12TextRenderer::RenderTextInternal(ID3D12GraphicsCommandList *list, floa
 
   RDCASSERT(strlen(text) < FONT_MAX_CHARS);
 
-  FontCBuffer data;
+  FontCBuffer data = {};
 
   data.TextPosition.x = x;
   data.TextPosition.y = y;
diff --git a/renderdoc/serialise/serialiser.h b/renderdoc/serialise/serialiser.h
index 74f78d5b6..4fdc98352 100644
--- a/renderdoc/serialise/serialiser.h
+++ b/renderdoc/serialise/serialiser.h
@@ -1572,7 +1572,7 @@ private:
   }
 
   void *m_pUserData = NULL;
-  uint64_t m_Version;
+  uint64_t m_Version = 0;
 
   uint64_t m_StructArg = 0;