diff --git a/src/core/bitmath_func.cpp b/src/core/bitmath_func.cpp
index 65188c9fd8..04c2e35b10 100644
--- a/src/core/bitmath_func.cpp
+++ b/src/core/bitmath_func.cpp
@@ -55,6 +55,13 @@ uint8 FindFirstBit(uint32 x)
 	return pos;
 }
 
+uint8 FindFirstBit64(uint64 x)
+{
+	if (x == 0) return 0;
+	if ((x & 0x00000000ffffffffULL) != 0) return FindFirstBit(x);
+	return FindFirstBit(x >> 32) + 32;
+}
+
 #endif
 
 /**
diff --git a/src/core/bitmath_func.hpp b/src/core/bitmath_func.hpp
index 2d908130b8..5bbb4ca016 100644
--- a/src/core/bitmath_func.hpp
+++ b/src/core/bitmath_func.hpp
@@ -198,6 +198,13 @@ inline uint8 FindFirstBit(uint32 x)
 	return __builtin_ctz(x);
 }
 
+inline uint8 FindFirstBit64(uint64 x)
+{
+	if (x == 0) return 0;
+
+	return __builtin_ctzll(x);
+}
+
 #else
 
 /** Lookup table to check which bit is set in a 6 bit variable */