diff --git a/src/units.cpp b/src/units.cpp
index 87bbd9b73..8a489cd26 100644
--- a/src/units.cpp
+++ b/src/units.cpp
@@ -370,12 +370,12 @@ void Units::unitAttributes(size_t index, std::string &reference, std::string &pr
     reference = u.mReference;
     prefix = u.mPrefix;
     if (!u.mExponent.empty()) {
-        exponent = std::stod(u.mExponent);
+        exponent = convertToDouble(u.mExponent);
     } else {
         exponent = 1.0;
     }
     if (!u.mMultiplier.empty()) {
-        multiplier = std::stod(u.mMultiplier);
+        multiplier = convertToDouble(u.mMultiplier);
     } else {
         multiplier = 1.0;
     }
diff --git a/src/utilities.cpp b/src/utilities.cpp
index 00f41f49a..c3cf3746e 100644
--- a/src/utilities.cpp
+++ b/src/utilities.cpp
@@ -34,13 +34,14 @@ namespace libcellml {
 
 double convertToDouble(const std::string &candidate)
 {
-    double value = 0.0;
     try {
-        value = std::stod(candidate);
+        return std::stod(candidate);
     } catch (...) {
-        value = std::numeric_limits<double>::infinity();
+        if (*candidate.begin() == '-') {
+            return -std::numeric_limits<double>::infinity();
+        }
+        return std::numeric_limits<double>::infinity();
     }
-    return value;
 }
 
 bool hasNonWhitespaceCharacters(const std::string &input)
diff --git a/tests/parser/parser.cpp b/tests/parser/parser.cpp
index df17443df..db116259c 100644
--- a/tests/parser/parser.cpp
+++ b/tests/parser/parser.cpp
@@ -582,6 +582,7 @@ TEST(Parser, modelWithInvalidUnits)
         "    <unit multiplier=\"Z\" exponent=\"35.0E+310\" units=\"kelvin\" bill=\"murray\">\n"
         "      <degrees/>\n"
         "    </unit>\n"
+        "    <unit exponent=\"-35.0E+310\" units=\"kelvin\"/>\n"
         "    <bobshouse address=\"34 Rich Lane\"/>\n"
         "    <unit GUnit=\"50c\"/>\n"
         "  </units>\n"
@@ -596,6 +597,7 @@ TEST(Parser, modelWithInvalidUnits)
         "<model xmlns=\"http://www.cellml.org/cellml/2.0#\" name=\"model_name\">\n"
         "  <units name=\"fahrenheitish\">\n"
         "    <unit exponent=\"inf\" units=\"kelvin\"/>\n"
+        "    <unit exponent=\"-inf\" units=\"kelvin\"/>\n"
         "    <unit units=\"\"/>\n"
         "  </units>\n"
         "  <units>\n"