diff --git a/include/chipmunk/chipmunk_structs.h b/include/chipmunk/chipmunk_structs.h
index 1485795d..20c9c001 100644
--- a/include/chipmunk/chipmunk_structs.h
+++ b/include/chipmunk/chipmunk_structs.h
@@ -239,12 +239,14 @@ typedef void (*cpConstraintPreStepImpl)(cpConstraint *constraint, cpFloat dt);
 typedef void (*cpConstraintApplyCachedImpulseImpl)(cpConstraint *constraint, cpFloat dt_coef);
 typedef void (*cpConstraintApplyImpulseImpl)(cpConstraint *constraint, cpFloat dt);
 typedef cpFloat (*cpConstraintGetImpulseImpl)(cpConstraint *constraint);
+typedef void (*cpConstraintResetAccImpl)(cpConstraint *constraint);
 
 typedef struct cpConstraintClass {
 	cpConstraintPreStepImpl preStep;
 	cpConstraintApplyCachedImpulseImpl applyCachedImpulse;
 	cpConstraintApplyImpulseImpl applyImpulse;
 	cpConstraintGetImpulseImpl getImpulse;
+	cpConstraintResetAccImpl resetAcc;
 } cpConstraintClass;
 
 struct cpConstraint {
diff --git a/src/cpBody.c b/src/cpBody.c
index 4ba4b494..d4cd89a6 100644
--- a/src/cpBody.c
+++ b/src/cpBody.c
@@ -160,6 +160,23 @@ cpBodySetType(cpBody *body, cpBodyType type)
 		body->m_inv = body->i_inv = INFINITY;
 		
 		cpBodyAccumulateMassFromShapes(body);
+
+        // Check any constraints, and if there are
+        // constraints with another non-DYNAMIC body:
+        // Reset any accumulated force in constraints attached to the body.
+        // Reset velocity of the body. These will be NaN or Inf otherwise.
+        cpConstraint* constraint = body->constraintList;
+        while (constraint) {
+            constraint->klass->resetAcc(constraint);
+            cpBody* a = cpConstraintGetBodyA(constraint);
+            a->v = cpvzero;
+            a->w = 0.0f;
+            cpBody* b = cpConstraintGetBodyB(constraint);
+            b->v = cpvzero;
+            b->w = 0.0f;
+
+            constraint = cpConstraintNext(constraint, body);
+        }
 	} else {
 		body->m = body->i = INFINITY;
 		body->m_inv = body->i_inv = 0.0f;
diff --git a/src/cpDampedRotarySpring.c b/src/cpDampedRotarySpring.c
index 8d38a545..32f7fb53 100644
--- a/src/cpDampedRotarySpring.c
+++ b/src/cpDampedRotarySpring.c
@@ -77,11 +77,18 @@ getImpulse(cpDampedRotarySpring *spring)
 	return spring->jAcc;
 }
 
+static void
+resetAcc(cpDampedRotarySpring *spring) 
+{
+	spring->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpDampedRotarySpring *
diff --git a/src/cpDampedSpring.c b/src/cpDampedSpring.c
index e4d019e9..c057abed 100644
--- a/src/cpDampedSpring.c
+++ b/src/cpDampedSpring.c
@@ -82,11 +82,18 @@ getImpulse(cpDampedSpring *spring)
 	return spring->jAcc;
 }
 
+static void
+resetAcc(cpDampedSpring *spring)
+{
+	spring->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpDampedSpring *
diff --git a/src/cpGearJoint.c b/src/cpGearJoint.c
index 3670173b..57e91282 100644
--- a/src/cpGearJoint.c
+++ b/src/cpGearJoint.c
@@ -74,11 +74,18 @@ getImpulse(cpGearJoint *joint)
 	return cpfabs(joint->jAcc);
 }
 
+static void
+resetAcc(cpGearJoint *joint)
+{
+	joint->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpGearJoint *
diff --git a/src/cpGrooveJoint.c b/src/cpGrooveJoint.c
index 50d1857d..56cecf2e 100644
--- a/src/cpGrooveJoint.c
+++ b/src/cpGrooveJoint.c
@@ -103,11 +103,18 @@ getImpulse(cpGrooveJoint *joint)
 	return cpvlength(joint->jAcc);
 }
 
+static void
+resetAcc(cpGrooveJoint *joint)
+{
+	joint->jAcc = cpvzero;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpGrooveJoint *
diff --git a/src/cpPinJoint.c b/src/cpPinJoint.c
index 545e78bf..d4f7b111 100644
--- a/src/cpPinJoint.c
+++ b/src/cpPinJoint.c
@@ -80,14 +80,20 @@ getImpulse(cpPinJoint *joint)
 	return cpfabs(joint->jnAcc);
 }
 
+static void
+resetAcc(cpPinJoint *joint)
+{
+	joint->jnAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
-
 cpPinJoint *
 cpPinJointAlloc(void)
 {
diff --git a/src/cpPivotJoint.c b/src/cpPivotJoint.c
index e45ba072..44f215df 100644
--- a/src/cpPivotJoint.c
+++ b/src/cpPivotJoint.c
@@ -70,9 +70,15 @@ applyImpulse(cpPivotJoint *joint, cpFloat dt)
 }
 
 static cpFloat
-getImpulse(cpConstraint *joint)
+getImpulse(cpPivotJoint *joint)
 {
-	return cpvlength(((cpPivotJoint *)joint)->jAcc);
+	return cpvlength(joint->jAcc);
+}
+
+static void
+resetAcc(cpPivotJoint *joint)
+{
+	joint->jAcc = cpvzero;
 }
 
 static const cpConstraintClass klass = {
@@ -80,6 +86,7 @@ static const cpConstraintClass klass = {
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpPivotJoint *
diff --git a/src/cpRatchetJoint.c b/src/cpRatchetJoint.c
index b3c9687e..0344f4f6 100644
--- a/src/cpRatchetJoint.c
+++ b/src/cpRatchetJoint.c
@@ -94,11 +94,18 @@ getImpulse(cpRatchetJoint *joint)
 	return cpfabs(joint->jAcc);
 }
 
+static void
+resetAcc(cpRatchetJoint *joint)
+{
+	joint->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpRatchetJoint *
diff --git a/src/cpRotaryLimitJoint.c b/src/cpRotaryLimitJoint.c
index 548adbeb..2710b827 100644
--- a/src/cpRotaryLimitJoint.c
+++ b/src/cpRotaryLimitJoint.c
@@ -91,11 +91,18 @@ getImpulse(cpRotaryLimitJoint *joint)
 	return cpfabs(joint->jAcc);
 }
 
+static void
+resetAcc(cpRotaryLimitJoint *joint)
+{
+	joint->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpRotaryLimitJoint *
diff --git a/src/cpSimpleMotor.c b/src/cpSimpleMotor.c
index 2bea74a5..cda6a602 100644
--- a/src/cpSimpleMotor.c
+++ b/src/cpSimpleMotor.c
@@ -70,11 +70,18 @@ getImpulse(cpSimpleMotor *joint)
 	return cpfabs(joint->jAcc);
 }
 
+static void
+resetAcc(cpSimpleMotor *joint)
+{
+	joint->jAcc = 0.0f;
+}
+
 static const cpConstraintClass klass = {
 	(cpConstraintPreStepImpl)preStep,
 	(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
 	(cpConstraintApplyImpulseImpl)applyImpulse,
 	(cpConstraintGetImpulseImpl)getImpulse,
+	(cpConstraintResetAccImpl)resetAcc,
 };
 
 cpSimpleMotor *
diff --git a/src/cpSlideJoint.c b/src/cpSlideJoint.c
index 61afe33e..7279867a 100644
--- a/src/cpSlideJoint.c
+++ b/src/cpSlideJoint.c
@@ -89,9 +89,15 @@ applyImpulse(cpSlideJoint *joint, cpFloat dt)
 }
 
 static cpFloat
-getImpulse(cpConstraint *joint)
+getImpulse(cpSlideJoint *joint)
 {
-	return cpfabs(((cpSlideJoint *)joint)->jnAcc);
+	return cpfabs(joint->jnAcc);
+}
+
+static void
+resetAcc(cpSlideJoint *joint)
+{
+	joint->jnAcc = 0.0f;
 }
 
 static const cpConstraintClass klass = {