diff --git a/native/src/defines.h b/native/src/defines.h
index 119a7d7..096f1fb 100644
--- a/native/src/defines.h
+++ b/native/src/defines.h
@@ -169,6 +169,7 @@
 #define NOT_VALID_WORD -99
 #define NOT_A_CHARACTER -1
 #define NOT_A_DISTANCE -1
+#define NOT_A_COORDINATE -1
 #define EQUIVALENT_CHAR_WITHOUT_DISTANCE_INFO -2
 #define PROXIMITY_CHAR_WITHOUT_DISTANCE_INFO -3
 #define NOT_A_INDEX -1
diff --git a/native/src/proximity_info.cpp b/native/src/proximity_info.cpp
index b91957c..e0e9380 100644
--- a/native/src/proximity_info.cpp
+++ b/native/src/proximity_info.cpp
@@ -165,6 +165,9 @@
     if (!hasSweetSpotData(keyIndex)) {
         return NOT_A_DISTANCE_FLOAT;
     }
+    if (NOT_A_COORDINATE == mInputXCoordinates[inputIndex]) {
+        return NOT_A_DISTANCE_FLOAT;
+    }
     const float squaredDistance = calculateSquaredDistanceFromSweetSpotCenter(keyIndex, inputIndex);
     const float squaredRadius = square(mSweetSpotRadii[keyIndex]);
     return squaredDistance / squaredRadius;