diff --git a/source/source_pw/module_pwdft/soc.cpp b/source/source_pw/module_pwdft/soc.cpp
index a44a0b6a48..f5837f8e32 100644
--- a/source/source_pw/module_pwdft/soc.cpp
+++ b/source/source_pw/module_pwdft/soc.cpp
@@ -27,7 +27,9 @@ void Fcoef::create(const int i1, const int i2, const int i3)
     }
     else
     {
-        std::cout << "not allowed!" << std::endl;
+        std::cout << "Fcoef::create received invalid dimensions: "
+		  << "i1=" << i1 << ", i2=" << i2 << ", i3=" << i3
+		  << ". All dimensions must be positive." << std::endl;
     }
 
     return;
@@ -188,4 +190,4 @@ void Soc::set_fcoef(const int &l1,
         coeff += rotylm(m1, mi) * spinor(l1, j1, m, is1) * conj(rotylm(m2, mj)) * spinor(l2, j2, m, is2);
     }
     this->fcoef(it, is1, is2, ip1, ip2) = coeff;
-}
\ No newline at end of file
+}