diff --git a/src/IPhreeqc.cpp b/src/IPhreeqc.cpp
index 0f201060..e9512a0d 100644
--- a/src/IPhreeqc.cpp
+++ b/src/IPhreeqc.cpp
@@ -879,7 +879,7 @@ void IPhreeqc::SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, cha
 	this->PhreeqcPtr->register_fortran_basic_callback(fcn);
 }
 #else
-void IPhreeqc::SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, char *str))
+void IPhreeqc::SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, char *str, int l))
 {
 	this->PhreeqcPtr->register_fortran_basic_callback(fcn);
 }
diff --git a/src/IPhreeqc.h b/src/IPhreeqc.h
index f2758f51..3d4d008b 100644
--- a/src/IPhreeqc.h
+++ b/src/IPhreeqc.h
@@ -1666,7 +1666,7 @@ Headings
 #ifdef IPHREEQC_NO_FORTRAN_MODULE
 	IPQ_DLL_EXPORT IPQ_RESULT  SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str, size_t l));
 #else
-	IPQ_DLL_EXPORT IPQ_RESULT  SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str));
+	IPQ_DLL_EXPORT IPQ_RESULT  SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str, int l));
 #endif
 
 
diff --git a/src/IPhreeqc.hpp b/src/IPhreeqc.hpp
index cbd4efe8..f4060825 100644
--- a/src/IPhreeqc.hpp
+++ b/src/IPhreeqc.hpp
@@ -713,7 +713,7 @@ public:
 #ifdef IPHREEQC_NO_FORTRAN_MODULE
 	void                     SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, char *str, size_t l));
 #else
-	void                     SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, char *str));
+	void                     SetBasicFortranCallback(double (*fcn)(double *x1, double *x2, char *str, int l));
 #endif
 
 	/**
diff --git a/src/IPhreeqcLib.cpp b/src/IPhreeqcLib.cpp
index 13fbe98a..46e8d893 100644
--- a/src/IPhreeqcLib.cpp
+++ b/src/IPhreeqcLib.cpp
@@ -795,7 +795,7 @@ SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str,
 }
 #else
 IPQ_RESULT
-SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str))
+SetBasicFortranCallback(int id, double (*fcn)(double *x1, double *x2, char *str, int l))
 {
 	IPhreeqc* IPhreeqcPtr = IPhreeqcLib::GetInstance(id);
 	if (IPhreeqcPtr)
diff --git a/src/IPhreeqc_interface.F90 b/src/IPhreeqc_interface.F90
index 61fe2609..8164114b 100644
--- a/src/IPhreeqc_interface.F90
+++ b/src/IPhreeqc_interface.F90
@@ -853,22 +853,24 @@ INTEGER FUNCTION SetBasicFortranCallback(id, fcn)
 			IMPLICIT NONE
             INTEGER(KIND=C_INT), INTENT(in) :: id
             INTERFACE
-                REAL(KIND=C_DOUBLE) FUNCTION fcn(x1, x2, str) BIND(C)
+                REAL(KIND=C_DOUBLE) FUNCTION fcn(x1, x2, str, l) BIND(C)
                     USE ISO_C_BINDING
                     IMPLICIT none
                     REAL(KIND=C_DOUBLE), INTENT(in) :: x1, x2
                     CHARACTER(KIND=C_CHAR), INTENT(in) :: str(*)
+                    INTEGER(KIND=C_INT), INTENT(in) :: l
                 END FUNCTION fcn
            END INTERFACE
         END FUNCTION SetBasicFortranCallbackF
     END INTERFACE
     INTEGER, INTENT(in) :: id     
     INTERFACE
-        REAL(KIND=C_DOUBLE) FUNCTION fcn(x1, x2, str) BIND(C)
+        REAL(KIND=C_DOUBLE) FUNCTION fcn(x1, x2, str, l) BIND(C)
             USE ISO_C_BINDING
             IMPLICIT none
             REAL(KIND=C_DOUBLE), INTENT(in) :: x1, x2
             CHARACTER(KIND=C_CHAR), INTENT(in) :: str(*)
+            INTEGER(KIND=C_INT), INTENT(in) :: l
         END FUNCTION fcn
     END INTERFACE
 	SetBasicFortranCallback = SetBasicFortranCallbackF(id, fcn)
diff --git a/src/IPhreeqc_interface_F.cpp b/src/IPhreeqc_interface_F.cpp
index b40b5ed8..2f8f24fd 100644
--- a/src/IPhreeqc_interface_F.cpp
+++ b/src/IPhreeqc_interface_F.cpp
@@ -410,7 +410,7 @@ SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *st
 }
 #else
 IPQ_RESULT
-SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *str))
+SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *str, int l))
 {
 	return ::SetBasicFortranCallback(*id, fcn);
 }
diff --git a/src/IPhreeqc_interface_F.h b/src/IPhreeqc_interface_F.h
index f594f956..2dde6160 100644
--- a/src/IPhreeqc_interface_F.h
+++ b/src/IPhreeqc_interface_F.h
@@ -136,7 +136,7 @@ extern "C" {
 #ifdef IPHREEQC_NO_FORTRAN_MODULE
   IPQ_DLL_EXPORT IPQ_RESULT SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *str, size_t l));
 #else
-  IPQ_DLL_EXPORT IPQ_RESULT SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *str));
+  IPQ_DLL_EXPORT IPQ_RESULT SetBasicFortranCallbackF(int *id, double (*fcn)(double *x1, double *x2, char *str, int l));
 #endif
   IPQ_DLL_EXPORT IPQ_RESULT SetCurrentSelectedOutputUserNumberF(int *id, int *n);
   IPQ_DLL_EXPORT IPQ_RESULT SetDumpFileNameF(int *id, char* fname);