diff --git a/gtsam/linear/linearExceptions.cpp b/gtsam/linear/linearExceptions.cpp
index f633df4ce..0b0152026 100644
--- a/gtsam/linear/linearExceptions.cpp
+++ b/gtsam/linear/linearExceptions.cpp
@@ -22,6 +22,22 @@
 
 namespace gtsam {
 
+  /* ************************************************************************* */
+  const char* IndeterminantLinearSystemException::what() const throw()
+  {
+    if(!description_)
+      description_ = String(
+          "\nIndeterminant linear system detected while working near variable with\n"
+          "index " + boost::lexical_cast<String>(j_) + " in ordering.\n"
+          "\n\
+Thrown when a linear system is ill-posed.  The most common cause for this\n\
+error is having underconstrained variables.  Mathematically, the system is\n\
+underdetermined.  See the GTSAM Doxygen documentation at\n\
+http://borg.cc.gatech.edu/ on gtsam::IndeterminantLinearSystemException for\n\
+more information.");
+    return description_->c_str();
+  }
+
   /* ************************************************************************* */
   const char* InvalidNoiseModel::what() const throw() {
     if(description_.empty())
diff --git a/gtsam/linear/linearExceptions.h b/gtsam/linear/linearExceptions.h
index 75df81e98..62f12cc2e 100644
--- a/gtsam/linear/linearExceptions.h
+++ b/gtsam/linear/linearExceptions.h
@@ -92,25 +92,13 @@ namespace gtsam {
      ordered in elimination order and occupy scalars in the same way as
      described for Jacobian columns in the previous bullet.
    */
-  class IndeterminantLinearSystemException : public ThreadsafeException<IndeterminantLinearSystemException> {
+  class GTSAM_EXPORT IndeterminantLinearSystemException : public ThreadsafeException<IndeterminantLinearSystemException> {
     Index j_;
   public:
     IndeterminantLinearSystemException(Index j) throw() : j_(j) {}
     virtual ~IndeterminantLinearSystemException() throw() {}
     Index nearbyVariable() const { return j_; }
-    virtual const char* what() const throw() {
-      if(!description_)
-        description_ = String(
-"\nIndeterminant linear system detected while working near variable with\n"
-"index " + boost::lexical_cast<String>(j_) + " in ordering.\n"
-"\n\
-Thrown when a linear system is ill-posed.  The most common cause for this\n\
-error is having underconstrained variables.  Mathematically, the system is\n\
-either underdetermined, or its quadratic error function is concave in some\n\
-directions.  See the GTSAM Doxygen documentation at http://borg.cc.gatech.edu/ \n\
-on gtsam::IndeterminantLinearSystemException for more information.");
-      return description_->c_str();
-    }
+    virtual const char* what() const throw();
   };
 
   /* ************************************************************************* */