diff --git a/CMakeModules/CompilerSettings.cmake b/CMakeModules/CompilerSettings.cmake
index e3c76d9fd..b2c0ee6fe 100644
--- a/CMakeModules/CompilerSettings.cmake
+++ b/CMakeModules/CompilerSettings.cmake
@@ -1,6 +1,6 @@
 # GCC
 if(CMAKE_COMPILER_IS_GNUCXX)
-    add_definitions(-std=c++11 -W -Wall -Wextra -Wpedantic -Wno-missing-field-initializers -Wno-unused-parameter)
+    add_definitions(-std=c++11 -W -Wall -Wextra -Wpedantic -Wno-unused-parameter)
     if(FCL_TREAT_WARNINGS_AS_ERRORS)
         add_definitions(-Werror)
     endif()
@@ -8,7 +8,7 @@ endif()
 
 # Clang
 if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    add_definitions(-std=c++11 -W -Wall -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Wno-delete-non-virtual-dtor -Wno-overloaded-virtual -Wno-deprecated-register)
+    add_definitions(-std=c++11 -W -Wall -Wextra -Wno-unused-parameter)
     if(FCL_TREAT_WARNINGS_AS_ERRORS)
         add_definitions(-Werror)
     endif()
@@ -20,7 +20,7 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
     if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.1)
         message(FATAL_ERROR "AppleClang version must be at least 6.1!")
     endif()
-    add_definitions(-std=c++11 -W -Wall -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Wno-delete-non-virtual-dtor -Wno-overloaded-virtual -Wno-deprecated-register)
+    add_definitions(-std=c++11 -W -Wall -Wextra -Wno-unused-parameter)
     if(FCL_TREAT_WARNINGS_AS_ERRORS)
         add_definitions(-Werror)
     endif()
diff --git a/include/fcl/math/bv/OBB-inl.h b/include/fcl/math/bv/OBB-inl.h
index 7560a79d0..0b9b132bc 100644
--- a/include/fcl/math/bv/OBB-inl.h
+++ b/include/fcl/math/bv/OBB-inl.h
@@ -391,7 +391,7 @@ template <typename S>
 bool obbDisjoint(const Matrix3<S>& B, const Vector3<S>& T,
                  const Vector3<S>& a, const Vector3<S>& b)
 {
-  register S t, s;
+  S t, s;
   const S reps = 1e-6;
 
   Matrix3<S> Bf = B.cwiseAbs();
@@ -521,7 +521,7 @@ bool obbDisjoint(
     const Vector3<S>& a,
     const Vector3<S>& b)
 {
-  register S t, s;
+  S t, s;
   const S reps = 1e-6;
 
   Matrix3<S> Bf = tf.linear().cwiseAbs();
diff --git a/include/fcl/math/motion/taylor_model/taylor_model-inl.h b/include/fcl/math/motion/taylor_model/taylor_model-inl.h
index ed83d09d0..2ebb086e6 100644
--- a/include/fcl/math/motion/taylor_model/taylor_model-inl.h
+++ b/include/fcl/math/motion/taylor_model/taylor_model-inl.h
@@ -275,8 +275,8 @@ template <typename S>
 TaylorModel<S>& TaylorModel<S>::operator *= (const TaylorModel<S>& other)
 {
   assert(other.time_interval_ == time_interval_);
-  register S c0, c1, c2, c3;
-  register S c0b = other.coeffs_[0], c1b = other.coeffs_[1], c2b = other.coeffs_[2], c3b = other.coeffs_[3];
+  S c0, c1, c2, c3;
+  S c0b = other.coeffs_[0], c1b = other.coeffs_[1], c2b = other.coeffs_[2], c3b = other.coeffs_[3];
 
   const Interval<S>& rb = other.r_;
 
@@ -286,7 +286,7 @@ TaylorModel<S>& TaylorModel<S>::operator *= (const TaylorModel<S>& other)
   c3 = coeffs_[0] * c3b + coeffs_[1] * c2b + coeffs_[2] * c1b + coeffs_[3] * c0b;
 
   Interval<S> remainder(r_ * rb);
-  register S tempVal = coeffs_[1] * c3b + coeffs_[2] * c2b + coeffs_[3] * c1b;
+  S tempVal = coeffs_[1] * c3b + coeffs_[2] * c2b + coeffs_[3] * c1b;
   remainder += time_interval_->t4_ * tempVal;
 
   tempVal = coeffs_[2] * c3b + coeffs_[3] * c2b;
@@ -368,12 +368,12 @@ Interval<S> TaylorModel<S>::getTightBound(S t0, S t1) const
 
   if(coeffs_[3] == 0)
   {
-    register S a = -coeffs_[1] / (2 * coeffs_[2]);
+    S a = -coeffs_[1] / (2 * coeffs_[2]);
     Interval<S> polybounds;
     if(a <= t1 && a >= t0)
     {
       S AQ = coeffs_[0] + a * (coeffs_[1] + a * coeffs_[2]);
-      register S t = t0;
+      S t = t0;
       S LQ = coeffs_[0] + t * (coeffs_[1] + t * coeffs_[2]);
       t = t1;
       S RQ = coeffs_[0] + t * (coeffs_[1] + t * coeffs_[2]);
@@ -392,7 +392,7 @@ Interval<S> TaylorModel<S>::getTightBound(S t0, S t1) const
     }
     else
     {
-      register S t = t0;
+      S t = t0;
       S LQ = coeffs_[0] + t * (coeffs_[1] + t * coeffs_[2]);
       t = t1;
       S RQ = coeffs_[0] + t * (coeffs_[1] + t * coeffs_[2]);
@@ -405,7 +405,7 @@ Interval<S> TaylorModel<S>::getTightBound(S t0, S t1) const
   }
   else
   {
-    register S t = t0;
+    S t = t0;
     S LQ = coeffs_[0] + t * (coeffs_[1] + t * (coeffs_[2] + t * coeffs_[3]));
     t = t1;
     S RQ = coeffs_[0] + t * (coeffs_[1] + t * (coeffs_[2] + t * coeffs_[3]));
diff --git a/include/fcl/narrowphase/distance-inl.h b/include/fcl/narrowphase/distance-inl.h
index 1372d279c..e27c1d8c9 100644
--- a/include/fcl/narrowphase/distance-inl.h
+++ b/include/fcl/narrowphase/distance-inl.h
@@ -162,7 +162,7 @@ typename NarrowPhaseSolver::S distance(
     collide(o1, tf1, o2, tf2, nsolver, collision_request, collision_result);
     assert(collision_result.isCollision());
 
-    std::size_t index = -1;
+    std::size_t index = static_cast<std::size_t>(-1);
     S max_pen_depth = std::numeric_limits<S>::min();
     for (auto i = 0u; i < collision_result.numContacts(); ++i)
     {