diff --git a/radiantcore/brush/TextureMatrix.cpp b/radiantcore/brush/TextureMatrix.cpp
index 533ecd7051..8c36224223 100644
--- a/radiantcore/brush/TextureMatrix.cpp
+++ b/radiantcore/brush/TextureMatrix.cpp
@@ -207,3 +207,13 @@ Matrix4 TextureMatrix::getTransform() const {
 
 	return transform;
 }
+
+bool TextureMatrix::isSane() const
+{
+    return !std::isnan(coords[0][0]) && !std::isinf(coords[0][0]) &&
+           !std::isnan(coords[0][1]) && !std::isinf(coords[0][1]) &&
+           !std::isnan(coords[0][2]) && !std::isinf(coords[0][2]) &&
+           !std::isnan(coords[1][0]) && !std::isinf(coords[1][0]) &&
+           !std::isnan(coords[1][1]) && !std::isinf(coords[1][1]) &&
+           !std::isnan(coords[1][2]) && !std::isinf(coords[1][2]);
+}
diff --git a/radiantcore/brush/TextureMatrix.h b/radiantcore/brush/TextureMatrix.h
index 05ccee4094..be960d722b 100644
--- a/radiantcore/brush/TextureMatrix.h
+++ b/radiantcore/brush/TextureMatrix.h
@@ -57,6 +57,9 @@ struct TextureMatrix
 	 * components, they are just copied into the right places.
 	 */
 	Matrix4 getTransform() const;
+
+    // Checks if any of the matrix components are NaN or INF (in which case the matrix is not sane)
+    bool isSane() const;
 };
 
 inline std::ostream& operator<<(std::ostream& st, const TextureMatrix& texdef)
diff --git a/radiantcore/brush/TextureProjection.cpp b/radiantcore/brush/TextureProjection.cpp
index 2acb2a57ae..6f65d58f76 100644
--- a/radiantcore/brush/TextureProjection.cpp
+++ b/radiantcore/brush/TextureProjection.cpp
@@ -177,7 +177,8 @@ void TextureProjection::fitTexture(std::size_t width, std::size_t height, const
         return;
     }
 
-    Matrix4 st2tex = getTransform();
+    // Sanity-check the matrix, if it contains any NaNs or INFs we fall back to the default projection (#5371)
+    Matrix4 st2tex = matrix.isSane() ? getTransform() : GetDefaultProjection().getTransform();
 
     // the current texture transform
     Matrix4 local2tex = st2tex;