diff --git a/al/source.h b/al/source.h
index 1499f347..c0281f3e 100644
--- a/al/source.h
+++ b/al/source.h
@@ -16,6 +16,7 @@
 #include "alu.h"
 #include "math_defs.h"
 #include "vector.h"
+#include "voice.h"
 
 struct ALbuffer;
 struct ALeffectslot;
diff --git a/al/state.cpp b/al/state.cpp
index 026f2808..ae761fb8 100644
--- a/al/state.cpp
+++ b/al/state.cpp
@@ -43,6 +43,7 @@
 #include "inprogext.h"
 #include "opthelpers.h"
 #include "strutils.h"
+#include "voice.h"
 
 
 namespace {
diff --git a/alc/alcontext.h b/alc/alcontext.h
index 4e2bcdd7..31160bb2 100644
--- a/alc/alcontext.h
+++ b/alc/alcontext.h
@@ -23,14 +23,15 @@
 #include "threads.h"
 #include "vecmat.h"
 #include "vector.h"
-#include "voice.h"
 
 struct ALeffectslot;
 struct ALsource;
 struct EffectSlot;
 struct EffectSlotProps;
 struct RingBuffer;
+struct Voice;
 struct VoiceChange;
+struct VoicePropsItem;
 
 
 enum class DistanceModel : unsigned char {
diff --git a/alc/effects/convolution.cpp b/alc/effects/convolution.cpp
index 79a63a38..716830a9 100644
--- a/alc/effects/convolution.cpp
+++ b/alc/effects/convolution.cpp
@@ -20,6 +20,7 @@
 #include "core/logging.h"
 #include "effects/base.h"
 #include "effectslot.h"
+#include "math_defs.h"
 #include "polyphase_resampler.h"
 
 
diff --git a/alc/effects/fshifter.cpp b/alc/effects/fshifter.cpp
index 630b8e1d..9fe3b77e 100644
--- a/alc/effects/fshifter.cpp
+++ b/alc/effects/fshifter.cpp
@@ -31,6 +31,8 @@
 #include "alcontext.h"
 #include "alu.h"
 #include "effectslot.h"
+#include "math_defs.h"
+
 
 namespace {
 
diff --git a/alc/effects/pshifter.cpp b/alc/effects/pshifter.cpp
index 0c8bdefc..ac00bac1 100644
--- a/alc/effects/pshifter.cpp
+++ b/alc/effects/pshifter.cpp
@@ -32,6 +32,7 @@
 #include "alnumeric.h"
 #include "alu.h"
 #include "effectslot.h"
+#include "math_defs.h"
 
 
 namespace {
diff --git a/alc/effects/vmorpher.cpp b/alc/effects/vmorpher.cpp
index 32c4b811..3bd4430c 100644
--- a/alc/effects/vmorpher.cpp
+++ b/alc/effects/vmorpher.cpp
@@ -29,6 +29,8 @@
 #include "alcontext.h"
 #include "alu.h"
 #include "effectslot.h"
+#include "math_defs.h"
+
 
 namespace {