diff --git a/src/classes/PFunction.cpp b/src/classes/PFunction.cpp
index b1f75b8f..c323d6dd 100644
--- a/src/classes/PFunction.cpp
+++ b/src/classes/PFunction.cpp
@@ -247,6 +247,8 @@ void PFunction::FillFuncEvalTree(iter_t const& i, PFuncTreeNode &node)
       node.fFunctionTag = FUN_LN;
     else if (!strcmp(str.c_str(), "EXP"))
       node.fFunctionTag = FUN_EXP;
+    else if (!strcmp(str.c_str(), "SQRT"))
+      node.fFunctionTag = FUN_SQRT;
     else {
       cerr << endl << "**PANIC ERROR**: function " << str << " doesn't exist, but you never should have reached this point!";
       cerr << endl;
@@ -442,11 +444,13 @@ Double_t PFunction::EvalNode(PFuncTreeNode &node)
     } else if (node.fFunctionTag == FUN_ATANH) {
       return atanh(EvalNode(node.children[0]));
     } else if (node.fFunctionTag == FUN_LOG) {
-      return log(EvalNode(node.children[0]))/log(10);
+      return log(EvalNode(node.children[0]))/log(10.0);
     } else if (node.fFunctionTag == FUN_LN) {
       return log(EvalNode(node.children[0]));
     } else if (node.fFunctionTag == FUN_EXP) {
       return exp(EvalNode(node.children[0]));
+    } else if (node.fFunctionTag == FUN_SQRT) {
+      return sqrt(EvalNode(node.children[0]));
     } else {
       cerr << endl << "**PANIC ERROR**: PFunction::EvalNode: node.fID == PFunctionGrammar::functionID: you never should have reached this point!";
       cerr << endl;
diff --git a/src/include/PFunction.h b/src/include/PFunction.h
index 1a5ca973..900cd592 100644
--- a/src/include/PFunction.h
+++ b/src/include/PFunction.h
@@ -69,6 +69,7 @@
 #define FUN_LOG   12
 #define FUN_LN    13
 #define FUN_EXP   14
+#define FUN_SQRT  15
 
 //----------------------------------------------------------------------------
 typedef struct func_tree_node {
diff --git a/src/include/PFunctionGrammar.h b/src/include/PFunctionGrammar.h
index 4dd752d5..cd4e2f46 100644
--- a/src/include/PFunctionGrammar.h
+++ b/src/include/PFunctionGrammar.h
@@ -105,6 +105,7 @@ struct PFunctionGrammar : public grammar<PFunctionGrammar>
                            |   lexeme_d[ root_node_d[ str_p("LOG")   ] >> ch_p('(') ] >> expression >> ch_p(')')
                            |   lexeme_d[ root_node_d[ str_p("LN")    ] >> ch_p('(') ] >> expression >> ch_p(')')
                            |   lexeme_d[ root_node_d[ str_p("EXP")   ] >> ch_p('(') ] >> expression >> ch_p(')')
+                           |   lexeme_d[ root_node_d[ str_p("SQRT")  ] >> ch_p('(') ] >> expression >> ch_p(')')
                            ;
 
             factor         =   real