diff --git a/src/sinqAxis.h b/src/sinqAxis.h
index d9c6a34..0ad4829 100644
--- a/src/sinqAxis.h
+++ b/src/sinqAxis.h
@@ -710,8 +710,7 @@ asynStatus getAxisParam(A *axis, C *controller, const char *indexName,
                         int (C::*func)(), char (*readValue)[N],
                         const char *callerFunctionName, int lineNumber) {
     return getAxisParamImpl(axis, controller, indexName, func, *readValue,
-                            callerFunctionName, lineNumber, sizeof(readValue),
-                            TypeTag<char>{});
+                            callerFunctionName, lineNumber, N, TypeTag<char>{});
 }
 
 /**