diff --git a/src.cmake b/src.cmake
index 44005aa041..daf96a588f 100644
--- a/src.cmake
+++ b/src.cmake
@@ -273,6 +273,7 @@ set(ENGINETESTLIST
     ${COMMON_DIR}/ColorTest.cpp
     ${COMMON_DIR}/StringTest.cpp
     ${COMMON_DIR}/cm/unittest.cpp
+    ${COMMON_DIR}/MathTest.cpp
     ${COMMON_DIR}/UtilTest.cpp
     ${ENGINE_DIR}/framework/CommandSystemTest.cpp
 )
diff --git a/src/common/Endian.h b/src/common/Endian.h
index 284e595631..c8276f709a 100644
--- a/src/common/Endian.h
+++ b/src/common/Endian.h
@@ -119,6 +119,12 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 # error The file boost/detail/endian.hpp needs to be set up for your CPU type.
 #endif
 
+// forward declaration
+namespace Util {
+	template<typename ToT, typename FromT>
+	ToT bit_cast(FromT from);
+}
+
 // Compilers are smart enough to optimize these to a single bswap instruction
 inline int16_t Swap16(int16_t x)
 {
diff --git a/src/common/Math.h b/src/common/Math.h
index 54ab4dfa59..2185fc0706 100644
--- a/src/common/Math.h
+++ b/src/common/Math.h
@@ -35,7 +35,8 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 namespace Math {
 
-    // Returns min if value is NaN
+    // This is designed to return min if value is NaN. That's not guaranteed to work when
+    // compiling with fast-math flags though.
     template<typename T> inline WARN_UNUSED_RESULT
     T Clamp(T value, T min, T max)
     {
@@ -47,6 +48,22 @@ namespace Math {
         return value;
     }
 
+    // IsFinite: Replacements for std::isfinite that should work even with fast-math flags
+
+    // An IEEE754 float is finite when the exponent is not all ones.
+    // 'volatile' serves as an optimization barrier against the compiler assuming that
+    // the float can never have a NaN bit pattern.
+    inline bool IsFinite(float x)
+    {
+        volatile uint32_t bits = Util::bit_cast<uint32_t>(x);
+        return ~bits & 0x7f800000;
+    }
+
+    inline bool IsFinite(double x)
+    {
+        volatile uint64_t bits = Util::bit_cast<uint64_t>(x);
+        return ~bits & 0x7ff0000000000000;
+    }
 }
 
 #include "math/Vector.h"
diff --git a/src/common/MathTest.cpp b/src/common/MathTest.cpp
new file mode 100644
index 0000000000..68394c0978
--- /dev/null
+++ b/src/common/MathTest.cpp
@@ -0,0 +1,66 @@
+/*
+===========================================================================
+Daemon BSD Source Code
+Copyright (c) 2024, Daemon Developers
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+    * Neither the name of the Daemon developers nor the
+      names of its contributors may be used to endorse or promote products
+      derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL DAEMON DEVELOPERS BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+===========================================================================
+*/
+
+#include <gtest/gtest.h>
+
+#include "common/Common.h"
+
+namespace Math {
+namespace {
+
+// Uncomment this and the tests should fail with GCC or Clang in release mode :-)
+//#define IsFinite std::isfinite
+
+TEST(IsFiniteTest, Float)
+{
+    ASSERT_TRUE(IsFinite(-0.0f));
+    ASSERT_TRUE(IsFinite(std::numeric_limits<float>::max()));
+    ASSERT_TRUE(IsFinite(std::numeric_limits<float>::min()));
+    ASSERT_TRUE(IsFinite(123.45f));
+
+    ASSERT_FALSE(IsFinite(std::stof("nan")));
+    ASSERT_FALSE(IsFinite(std::stof("inf")));
+    ASSERT_FALSE(IsFinite(std::stof("-inf")));
+}
+
+TEST(IsFiniteTest, Double)
+{
+    ASSERT_TRUE(IsFinite(-0.0));
+    ASSERT_TRUE(IsFinite(std::numeric_limits<double>::max()));
+    ASSERT_TRUE(IsFinite(std::numeric_limits<double>::min()));
+    ASSERT_TRUE(IsFinite(123.45));
+
+    ASSERT_FALSE(IsFinite(std::stod("nan")));
+    ASSERT_FALSE(IsFinite(std::stod("inf")));
+    ASSERT_FALSE(IsFinite(std::stod("-inf")));
+}
+
+} // namespace Math
+} // namespace
diff --git a/src/engine/audio/Audio.cpp b/src/engine/audio/Audio.cpp
index 68631387cd..f6a7d42412 100644
--- a/src/engine/audio/Audio.cpp
+++ b/src/engine/audio/Audio.cpp
@@ -82,7 +82,7 @@ namespace Audio {
     }
 
     bool IsValidVector(Vec3 v) {
-        return not std::isnan(v[0]) and not std::isnan(v[1]) and not std::isnan(v[2]);
+        return Math::IsFinite(v[0]) && Math::IsFinite(v[1]) && Math::IsFinite(v[2]);
     }
 
     bool Init() {
@@ -436,7 +436,7 @@ namespace Audio {
             return;
         }
 
-        if (slotNum < 0 or slotNum >= N_REVERB_SLOTS or std::isnan(ratio)) {
+        if (slotNum < 0 or slotNum >= N_REVERB_SLOTS or !Math::IsFinite(ratio)) {
             return;
         }
 
diff --git a/src/engine/audio/Emitter.cpp b/src/engine/audio/Emitter.cpp
index 042a2fc119..f94812e386 100644
--- a/src/engine/audio/Emitter.cpp
+++ b/src/engine/audio/Emitter.cpp
@@ -198,7 +198,7 @@ namespace Audio {
     void UpdateReverbSlot(int slotNum, std::string name, float ratio) {
         ASSERT_GE(slotNum, 0);
         ASSERT_LT(slotNum, N_REVERB_SLOTS);
-        ASSERT(!std::isnan(ratio));
+        ASSERT(Math::IsFinite(ratio));
 
         auto& slot = reverbSlots[slotNum];