diff --git a/src/libANGLE/renderer/vulkan/VertexArrayVk.cpp b/src/libANGLE/renderer/vulkan/VertexArrayVk.cpp
index c23d424b1a..082a4fcef3 100644
--- a/src/libANGLE/renderer/vulkan/VertexArrayVk.cpp
+++ b/src/libANGLE/renderer/vulkan/VertexArrayVk.cpp
@@ -306,6 +306,17 @@ size_t GetVertexCountForRange(GLint64 srcBufferBytes,
 
     size_t numVertices =
         static_cast<size_t>(srcBufferBytes + srcVertexStride - 1) / srcVertexStride;
+
+    // A vertex at stride-slot k occupies [k*stride, k*stride + formatSize). The ceil-division
+    // above can over-count by one when srcBufferBytes mod stride lies in [1, formatSize). Clamp
+    // so the last counted vertex's format-size read stays within srcBufferBytes. This mirrors
+    // the clamp already applied in CalculateMaxVertexCountForConversion.
+    size_t intendedSrcDataSize =
+        (numVertices - 1) * static_cast<size_t>(srcVertexStride) + srcFormatSize;
+    if (intendedSrcDataSize > static_cast<size_t>(srcBufferBytes))
+    {
+        numVertices = static_cast<size_t>(srcBufferBytes - srcFormatSize) / srcVertexStride + 1;
+    }
     return numVertices;
 }