--- a/src/MacSrc/OpenGL.cc
+++ b/src/MacSrc/OpenGL.cc
@@ -525,6 +525,13 @@
     bind_texture(s_uiTexture);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    // uiRgba is tightly packed, but gl4es implements GL_UNPACK_ROW_LENGTH/
+    // GL_UNPACK_ALIGNMENT client-side and persists whatever was last set
+    // across draw calls in the same context. Reset both to the packed
+    // defaults here so this upload doesn't inherit unrelated unpack state
+    // set elsewhere in the frame.
+    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, uiRgba->w, uiRgba->h, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                  uiRgba->pixels);