diff --git a/include/mitsuba/core/sse.h b/include/mitsuba/core/sse.h
index 9735c326..2baf9a80 100644
--- a/include/mitsuba/core/sse.h
+++ b/include/mitsuba/core/sse.h
@@ -51,6 +51,7 @@
 #ifndef MTS_SSE
 #define SSE_STR	"SSE2 disabled"
 #define enable_fpexcept_sse()
+#define query_fpexcept_sse() 0
 #define disable_fpexcept_sse()
 #else
 /* Include SSE intrinsics header file */
@@ -61,8 +62,9 @@
 #define splat_epi32(ps, i)       _mm_shuffle_epi32((ps), (i<<6) | (i<<4) | (i<<2) | i)
 #define mux_ps(sel, op1, op2)    _mm_or_ps   (_mm_and_ps   ((sel), (op1)), _mm_andnot_ps   ((sel), (op2)))
 #define mux_epi32(sel, op1, op2) _mm_or_si128(_mm_and_si128((sel), (op1)), _mm_andnot_si128((sel), (op2)))
-#define enable_fpexcept_sse()	 _MM_SET_EXCEPTION_MASK(_MM_GET_EXCEPTION_MASK() & ~(_MM_MASK_INVALID| _MM_MASK_DIV_ZERO))
-#define disable_fpexcept_sse()	 _MM_SET_EXCEPTION_MASK(_MM_GET_EXCEPTION_MASK() | (_MM_MASK_INVALID| _MM_MASK_DIV_ZERO))
+#define enable_fpexcept_sse()	 _MM_SET_EXCEPTION_MASK(_MM_GET_EXCEPTION_MASK() & ~(_MM_MASK_INVALID | _MM_MASK_DIV_ZERO))
+#define query_fpexcept_sse()	 (~_MM_GET_EXCEPTION_MASK() & (_MM_MASK_INVALID | _MM_MASK_DIV_ZERO))
+#define disable_fpexcept_sse()	 _MM_SET_EXCEPTION_MASK(_MM_GET_EXCEPTION_MASK() | (_MM_MASK_INVALID | _MM_MASK_DIV_ZERO))
 #define load1_epi32(i)           _mm_shuffle_epi32(_mm_cvtsi32_si128(i), 0)
 
 #ifdef __MSVC__
diff --git a/src/libcore/util.cpp b/src/libcore/util.cpp
index 3f4a17f7..fddeed0c 100644
--- a/src/libcore/util.cpp
+++ b/src/libcore/util.cpp
@@ -248,6 +248,11 @@ bool enableFPExceptions() {
 	exceptionsWereEnabled = ~cw & (_EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW);
 	cw &= ~(_EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW);
 	_controlfp(cw, _MCW_EM);
+#elif defined(__OSX__)
+#if !defined(MTS_SSE)
+#error SSE must be enabled to handle FP exceptions on OSX
+#endif
+	exceptionsWereEnabled = query_fpexcept_sse() != 0;
 #else
 	exceptionsWereEnabled = 
 		fegetexcept() & (FE_INVALID|FE_DIVBYZERO|FE_OVERFLOW);
@@ -267,6 +272,8 @@ bool disableFPExceptions() {
 	exceptionsWereEnabled = ~cw & (_EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW);
 	cw |= _EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW;
 	_controlfp(cw, _MCW_EM);
+#elif defined(__OSX__)
+	exceptionsWereEnabled = query_fpexcept_sse() != 0;
 #else
 	exceptionsWereEnabled = 
 		fegetexcept() & (FE_INVALID|FE_DIVBYZERO|FE_OVERFLOW);
@@ -283,6 +290,8 @@ void restoreFPExceptions(bool oldState) {
 #if defined(WIN32)
 	unsigned int cw = _controlfp(0, 0);
 	currentState = ~cw & (_EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW);
+#elif defined(__OSX__)
+	currentState = query_fpexcept_sse() != 0;
 #else
 	currentState = fegetexcept() & (FE_INVALID|FE_DIVBYZERO|FE_OVERFLOW);
 #endif
diff --git a/src/medium/heterogeneous-stencil.cpp b/src/medium/heterogeneous-stencil.cpp
index 8fc7b9e7..54fa6e6b 100644
--- a/src/medium/heterogeneous-stencil.cpp
+++ b/src/medium/heterogeneous-stencil.cpp
@@ -76,7 +76,7 @@ public:
 		if (m_albedo.get() == NULL)
 			Log(EError, "No albedo specified!");
 		if (m_orientations.get() == NULL)
-			Log(EError, "No orientations specified!");
+			Log(EWarn, "No orientations specified!");
 
 		if (m_shapes.size() != 0) {
 			m_kdTree->build();
@@ -86,10 +86,12 @@ public:
 		}
 
 		if (m_stepSize == 0) {
-			m_stepSize = std::min(std::min(
+			m_stepSize = std::min(
 				m_densities->getStepSize(),
-				m_albedo->getStepSize()),
-				m_orientations->getStepSize());
+				m_albedo->getStepSize());
+			if (m_orientations)
+				m_stepSize = std::min(m_stepSize,
+					m_orientations->getStepSize());
 
 			if (m_stepSize == std::numeric_limits<Float>::infinity()) 
 				Log(EError, "Unable to infer step size, please specify!");
@@ -329,7 +331,8 @@ public:
 		mRec.sigmaS = currentAlbedo * currentSigmaT;
 		mRec.sigmaA = Spectrum(currentSigmaT) - mRec.sigmaS;
 		mRec.albedo = currentAlbedo.max();
-		mRec.orientation = m_orientations->lookupVector(mRec.p);
+		mRec.orientation = m_orientations.get() 
+			? m_orientations->lookupVector(mRec.p) : Vector(0.0f);
 		mRec.medium = this;
 		return true;
 	}