diff --git a/src/Makevars.in b/src/Makevars.in
index bc8af66..29d5fb6 100644
--- a/src/Makevars.in
+++ b/src/Makevars.in
@@ -1,5 +1,3 @@
 PKG_CPPFLAGS = -DARMA_32BIT_WORD -I../inst/include/ -DRSPARSE_R_PKG -DARMA_NO_DEBUG
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
 PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) @FLOAT_LIBS@ $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
-
-CXX_STD = CXX11
diff --git a/src/Makevars.win b/src/Makevars.win
index 2cf0426..28faff0 100644
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -4,5 +4,3 @@ FLOAT_LIBS = $(shell ${R_SCMD} "float:::ldflags()")
 PKG_CPPFLAGS = -I../inst/include/ -DARMA_32BIT_WORD -DARMA_DONT_USE_BLAS -DARMA_NO_DEBUG -DRSPARSE_R_PKG
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
 PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) $(FLOAT_LIBS) $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
-
-CXX_STD = CXX11
diff --git a/src/utils.cpp b/src/utils.cpp
index ac0af28..f42e3e3 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -113,16 +113,17 @@ const std::string currentDateTime() {
 }
 
 arma::fmat extract_float_matrix(Rcpp::S4 x) {
-  Rcpp::IntegerMatrix x_data = x.slot("Data");
-  float* ptr = reinterpret_cast<float*>(&x_data[0]);
-  arma::fmat x_mapped = arma::fmat(ptr, x_data.nrow(), x_data.ncol(), false, true);
+  SEXP x_data = x.slot("Data");
+  SEXP dims = Rf_getAttrib(x_data, R_DimSymbol);
+  float* ptr = reinterpret_cast<float*>(INTEGER(x_data));
+  arma::fmat x_mapped = arma::fmat(ptr, INTEGER(dims)[0], INTEGER(dims)[1], false, true);
   return (x_mapped);
 }
 
 arma::fvec extract_float_vector(Rcpp::S4 x) {
-  Rcpp::IntegerVector x_data = x.slot("Data");
-  float* ptr = reinterpret_cast<float*>(&x_data[0]);
-  arma::fvec x_mapped = arma::fvec(ptr, x_data.length(), false, true);
+  SEXP x_data = x.slot("Data");
+  float* ptr = reinterpret_cast<float*>(INTEGER(x_data));
+  arma::fvec x_mapped = arma::fvec(ptr, Rf_xlength(x_data), false, true);
   return (x_mapped);
 }