diff --git a/include/mitsuba/core/octree.h b/include/mitsuba/core/octree.h
index fa9f6b85..4c25abe9 100644
--- a/include/mitsuba/core/octree.h
+++ b/include/mitsuba/core/octree.h
@@ -175,7 +175,7 @@ protected:
 			uint32_t *temp, uint32_t *start, uint32_t *end) {
 		if (start == end) {
 			return NULL;
-		} else if (end-start < m_maxItems || depth > m_maxDepth) {
+		} else if ((uint32_t) (end-start) < m_maxItems || depth > m_maxDepth) {
 			OctreeNode *result = new OctreeNode();
 			result->count = (uint32_t) (end-start);
 			result->offset = (uint32_t) (start-base);
diff --git a/src/utils/tonemap.cpp b/src/utils/tonemap.cpp
index 10066db8..f16d3833 100644
--- a/src/utils/tonemap.cpp
+++ b/src/utils/tonemap.cpp
@@ -93,9 +93,9 @@ public:
 					  angle = radToDeg(std::atan(r * halfLength)),
 					  tmp   = angle + 0.02f,
 				      f0 = 2.61e6f * math::fastexp(-2500*angle*angle),
-				      f1 = 20.91 / (tmp*tmp*tmp),
-				      f2 = 72.37 / (tmp*tmp),
-				      f  = 0.384f*f0 + 0.478*f1 + 0.138*f2;
+				      f1 = 20.91f / (tmp*tmp*tmp),
+				      f2 = 72.37f / (tmp*tmp),
+				      f  = 0.384f*f0 + 0.478f*f1 + 0.138f*f2;
 
 				*ptr++ = f;
 				sum += f;