diff --git a/R/IOFunctions.R b/R/IOFunctions.R
index d08087e1..f240a259 100644
--- a/R/IOFunctions.R
+++ b/R/IOFunctions.R
@@ -32,10 +32,10 @@ adjustOutputbyCPI <- function (outputyear, referenceyear, location_acronym, IsRo
 #' @return A matrix.
 normalizeIOTransactions <- function (IO_transactions_df, IO_output_df) {
   # Replace 0 in IO_transactions_df and IO_output_df with 1E-3 to avoid errors in solve(x_hat)
-  for (s in names(IO_output_df[IO_output_df == 0])){
+  for (s in names(IO_output_df[IO_output_df <= 0])){
     IO_transactions_df[s, s] <- 1E-3    
   }
-  IO_output_df[IO_output_df == 0] <- 1E-3
+  IO_output_df[IO_output_df <= 0] <- 1E-3
   Z <- as.matrix(IO_transactions_df)
   x <- unname(unlist(IO_output_df))
   x_hat <- diag(x, length(x), length(x))