diff --git a/doc/harp_iset.tex b/doc/harp_iset.tex
index 8a2134e4..f913efc8 100644
--- a/doc/harp_iset.tex
+++ b/doc/harp_iset.tex
@@ -314,8 +314,8 @@ format, which can be fixed point or floating point.
 \begin{tabular}{cl}
 \textbf{Instruction}&\textbf{Description}\\
 \hline
-\texttt{itof} \%dest, \%src&Integer to floating point.\\
-\texttt{ftoi} \%dest, \%src&Floating point to integer.\\
+\texttt{itof} \%dest, \%src&Signed integer to floating point.\\
+\texttt{ftoi} \%dest, \%src&Floating point to signed integer.\\
 \texttt{fneg} \%dest, \%src&Negate (complement sign bit).\\
 \texttt{fadd} \%dest, \%src1, \%src2&Floating point add.\\
 \texttt{fsub} \%dest, \%src1, \%src2&Floating point subtract.\\
diff --git a/src/instruction.cpp b/src/instruction.cpp
index 86f10695..0bd037ab 100644
--- a/src/instruction.cpp
+++ b/src/instruction.cpp
@@ -291,7 +291,7 @@ void Instruction::executeOn(Core &c) {
                    c.pc = c.shadowPc;
                  }
                  break;
-      case ITOF: reg[rdest] = Float(double(reg[rsrc[0]]), wordSz);
+      case ITOF: reg[rdest] = Float(double(Word_s(reg[rsrc[0]])), wordSz);
                  break; 
       case FTOI: reg[rdest] = Word_s(double(Float(reg[rsrc[0]], wordSz)));
                  reg[rdest].trunc(wordSz);
diff --git a/src/unit_test/float_test.cpp b/src/unit_test/float_test.cpp
index 8d5169a1..f432fd7b 100644
--- a/src/unit_test/float_test.cpp
+++ b/src/unit_test/float_test.cpp
@@ -24,6 +24,10 @@ int main() {
     for (unsigned i = 0; i < 2; i++) {
       int n = rand() - RAND_MAX/2;
       double d = n * 0.0000001;
+
+      // Sometimes do negative numbers.
+      if (rand() & 1) d = -d;
+
       try_val(d, sz);
     }